Problem:


Score : 500 points

Problem Statement

Given are N integers A_1,\ldots,A_N.

We will choose exactly K of these elements. Find the maximum possible product of the chosen elements.

Then, print the maximum product modulo (10^9+7), using an integer between 0 and 10^9+6 (inclusive).

Constraints

1 \leq K \leq N \leq 2\times 10^5

|A_i| \leq 10^9

Input

Input is given from Standard Input in the following format:

N K
A_1 \ldots A_N

Output

Print the maximum product modulo (10^9+7), using an integer between 0 and 10^9+6 (inclusive).

Sample Input 1

4 2
1 2 -3 -4

Sample Output 1

12

The possible products of the two chosen elements are 2, -3, -4, -6, -8, and 12, so the maximum product is 12.

Sample Input 2

4 3
-1 -2 -3 -4

Sample Output 2

1000000001

The possible products of the three chosen elements are -24, -12, -8, and -6, so the maximum product is -6.

We print this value modulo (10^9+7), that is, 1000000001.

Sample Input 3

2 1
-1 1000000000

Sample Output 3

1000000000

The possible products of the one chosen element are -1 and 1000000000, so the maximum product is 1000000000.

Sample Input 4

10 10
1000000000 100000000 10000000 1000000 100000 10000 1000 100 10 1

Sample Output 4

999983200

Be sure to print the product modulo (10^9+7).



Sample input:
4 2
1 2 -3 -4


Sample output:
12

Submission status: Accepted

Solution code:
n,k = map(int,input().split())
a = list(map(int,input().split()))
ans = 1
pls = 1
mod = 10**9+7
a_minu = [i for i in a if i <0]
if k==len(a):
    for i in range(k):
        ans *= a[i]
        ans %= mod
    print(ans)

elif len(a_minu)==len(a) and k%2==1:
    a.sort(reverse=True)
    for i in range(k):
        ans *= a[i]
        ans %= mod
    print(ans)

else:
    ani= 0
    anj= 0
    tmp = 0
    tmp2  = 0
    alis = []
    lasim = -1
    lasip = -1
    for i in a:
        if i<0:
            alis.append([-i,-1])
        else:
            alis.append([i,1])
    alis.sort(key=lambda x:x[0], reverse=True)
    for i in range(k):
        if alis[i][1]==-1:
            lasim =  i
        else:
            lasip = i
        ans *= alis[i][0]
        ans %= mod
        pls *= alis[i][1]
    if pls ==1:
        print(ans)
    else:
        ju= 0
        jud = 0
        if lasim >= 0:
            tmp = ans*pow(alis[lasim][0],mod-2,mod)
            for i in range(k,n):
                if alis[i][1]==-1:
                    continue
                else:
                    #print(alis[i][0],tmp)
                    tmp *= alis[i][0]
                    ju = 1
                    ani = alis[i][0]
                    break
            if ju==0:
                tmp = 0
        if lasip >= 0:
            tmp2 = ans*pow(alis[lasip][0],mod-2,mod)
            for i in range(k,n):
                if alis[i][1]==1:
                    continue
                else:
                    #print(alis[i][0],tmp2)
                    tmp2 *= alis[i][0]
                    jud = 1
                    anj = alis[i][0]
                    break
            if jud==0:
                tmp2 = 0

        if abs(alis[lasip][0]*ani)<=abs(alis[lasim][0]*anj):
            print(tmp2%mod)
        else:
            print(tmp%mod)

Submission status: Accepted

Solution code:
import sys


def solve(n, k, aaa):
    pos = []
    neg = []
    MOD = 10 ** 9 + 7
    for a in aaa:
        if a > 0:
            pos.append(a)
        elif a < 0:
            neg.append(a)
    if len(pos) + len(neg) < k:
        return 0
    if len(pos) == 0:
        if k % 2 == 1:
            if len(neg) < n:
                return 0
            neg.sort(reverse=True)
        else:
            neg.sort()
        ans = 1
        for a in neg[:k]:
            ans = ans * a % MOD
        return ans
    if len(pos) + len(neg) == k:
        if n > k and len(neg) % 2 == 1:
            return 0
        ans = 1
        for a in pos:
            ans = ans * a % MOD
        for a in neg:
            ans = ans * a % MOD
        return ans

    pos.sort()
    neg.sort(reverse=True)
    ans = 1
    r = k

    if r % 2 == 1:
        ans = ans * pos.pop() % MOD
        r -= 1

    while r >= 2:
        if len(pos) <= 1:
            ans = ans * neg.pop() * neg.pop() % MOD
        elif len(neg) <= 1:
            ans = ans * pos.pop() * pos.pop() % MOD
        else:
            pm = pos[-1] * pos[-2]
            nm = neg[-1] * neg[-2]
            if pm > nm:
                ans = ans * pm % MOD
                pos.pop()
                pos.pop()
            else:
                ans = ans * nm % MOD
                neg.pop()
                neg.pop()
        r -= 2

    return ans


n, k, *aaa = map(int, sys.stdin.buffer.read().split())
print(solve(n, k, aaa))

Submission status: Accepted

Solution code:
from heapq import *
import sys
from collections import *
from itertools import *
from decimal import *
import copy
from bisect import *
import math
sys.setrecursionlimit(4100000)
def gcd(a,b):
    if(a%b==0):return(b)
    return (gcd(b,a%b))
input=lambda :sys.stdin.readline().rstrip()
N,K=map(int,input().split())

A=list(map(int,input().split()))
mod=10**9+7
Am=[-i for i in A if i<0]
Ap=[i for i in A if i>=0]

Am.sort()
Ap.sort()
Am=deque(Am)
Ap=deque(Ap)



if N==K:
    c=1
    for a in A:
        c*=a
        c%=mod

elif len(Ap)==0 and K%2:
    c=1
    while K :
        c*=Am.popleft()

        K-=1

        c%=mod
    c=-c
    c%=mod
    #print("unko")

else:
    #print(unko)
    c=1
    h=0
    a="unko"
    b="unko"
    while K and (Am or Ap) :
        if Am and Ap:
            if Am[-1]>Ap[-1]:

                a=Am.pop()
                c*=a
                h+=1
            else:

                b=Ap.pop()
                c*=b

        elif Am:
            a=Am.pop()
            c*=a
            h+=1
        elif Ap:
            b=Ap.pop()
            c*=b
        K-=1
        c%=mod

    if h%2:
        if Am and Ap and a!="unko" and b!="unko":
            if Am[-1]*a>Ap[-1]*b:
                a=Am.pop()
                c*=a
                c*=pow(b,mod-2,mod)
            else:
                b=Ap.pop()
                c*=b
                c*=pow(a,mod-2,mod)
        elif Am and b!="unko":
            a=Am.pop()
            c*=a
            c*=pow(b,mod-2,mod)
        else:
            b=Ap.pop()
            c*=b
            c*=pow(a,mod-2,mod)


print(c%mod)

Submission status: Accepted

Solution code:
from collections import deque
import math

def Next(): return input()
def NextInt(): return int(Next())
def NextInts(): return map(int,input().split())
def Nexts(): return map(str,input().split())
def NextIntList(): return list(map(int,input().split()))
def RowInts(n): return [input() for i in range(n)]

def solve():
    n, k = NextInts()
    da = NextIntList()
    ans = 1
    MOD = 10**9+7
    
    if n == k:
        for i in range(n):
            ans = ans*da[i]%MOD
        return ans
    
    neg = []
    pos = []
    for i in range(n):
        if da[i] < 0:
            neg.append(da[i])
        else:
            pos.append(da[i])
    neg.sort()
    pos.sort()

    if len(pos) == 0 and k%2 == 1:
        neg.reverse()
        for i in range(k):
            ans = ans * neg[i] % MOD
        return ans
    
    pos.reverse()
    li = []
    po, ne = 0, 0
    if k%2 == 1:
        po = 1
        ans = pos[0]
    while po+1 < len(pos):
        li.append(pos[po]*pos[po+1])
        po += 2
    while ne+1 < len(neg):
        li.append(neg[ne]*neg[ne+1])
        ne += 2
    li.sort()
    li.reverse()
    for i in range(k//2):
        ans = li[i] * ans % MOD
    return ans

if __name__ == "__main__":
    print(solve())

Submission status: Accepted

Solution code:
n,k=map(int,input().split())
a=[0]*n
a=list(map(int,input().split()))
a=sorted(a)
mod=10**9+7
ans=1

if (k%2==0 or a[-1]>=0):
    mlt1=a[0]*a[1]
    mlt2=a[-2]*a[-1]
    l=0
    r=-1
    for i in range(k//2):
        if (mlt1>=mlt2):
            ans*=mlt1%mod
            l+=2
            if (l<=n-2):
                mlt1=a[l+1]*a[l]
        else:
            ans*=mlt2%mod
            r-=2
            if (r>=-n+1):
                mlt2=a[r-1]*a[r]
        ans%=mod
    if (k%2==1):
        ans*=a[r]
        ans%=mod
    
else:
    for i in range(k):
        ans*=a[n-1-i]
        ans%=mod
        
print(ans)

Submission status: Accepted

Solution code:
def resolve():
    from bisect import bisect_left
    n,k=map(int,input().split())
    a=sorted(list(map(int,input().split())))
    m=bisect_left(a,0)
    MOD=10**9+7
    ans=1
    if m==0 or (m==n and k%2==1):
        for i in a[-k:]:
            ans=(ans*i)%MOD
    elif m==n and k%2==0:
        for i in a[:k]:
            ans=(ans*i)%MOD
    else:
        ans=1
        l,r=0,-1
        lm=a[0]*a[1]
        rm=a[-1]*a[-2]
        for i in range(k//2):
            if lm>=rm:
                ans*=lm%MOD
                l+=2
                if l<=n-2:
                    lm=a[l]*a[l+1]
            else:
                ans*=rm%MOD
                r-=2
                if 1<=n+r:
                    rm=a[r]*a[r-1]
            ans%=MOD
        if k%2==1:
            ans*=a[r]
            ans%=MOD
    print(ans)

if __name__ == '__main__':
    resolve()

Submission status: Accepted

Solution code:
import sys, math
N, K = map(int, input().split())
A = sorted(list(map(int, input().split())), key=lambda x: abs(x))[::-1]
P = int(1e9+7)
ans = 1
hu = None
sei = None
flg = False
for a in A:
    flg = a > 0
    if flg:
        break
if not flg:
    if K%2==1:
        for i in range(1, K+1):
            ans = (ans * A[-i]) % P
    else:
        for i in range(K):
            ans = (ans * A[i]) % P
    print(ans)
    sys.exit()
if K == N:
    for a in A:
        ans = (ans * a) % P
    print(ans)
    sys.exit()

for i, a in zip(range(K), A):
    if a > 0:
        if sei:
            ans = (ans * sei) % P
        sei = a
    else:
        if hu is None:
            hu = a
        else:
            ans = (ans * a * hu) % P
            hu = None

ptn1, ptn2 = -math.inf, -math.inf
if hu:
    if sei:
        for i in range(K, N):
            if A[i] > 0:
                ptn1 = sei * A[i]
                break
        for i in range(K, N):
            if A[i] <= 0:
                ptn2 = hu * A[i]
                break
        ans = (ans * max(ptn1, ptn2)) % P
    else:
        for i in range(K, N):
            if A[i] > 0:
                ans = (ans * A[i]) % P
                break
else:
    if sei:
        ans = (ans * sei) % P
print(ans % P)

Submission status: Accepted

Solution code:
from collections import deque
n,k = map(int,input().split())
a = list(map(int,input().split()))
mod = 10**9+7
p = []
m = []
ans = 1
for i in a:
    if i < 0:
        m.append(-i)
    else:
        p.append(i)
cp = len(p)
cm = len(m)
m.append(0)
m.append(0)
p.append(0)
p.append(0)
p.sort()
m.sort()
p = deque(p)
m = deque(m)
if cm == n and k%2 == 1:
    f = 1
else:
    f = 0 
if f == 0:
    while k:
        # print(k,cm,m)
        if k%2 == 1 and cp:
            p1 = deque.pop(p)
            ans *= p1
            k -= 1
            cp -= 1
        elif f == 0 and m[-1] * m[-2] > p[-1] * p[-2] and cm > 1 and k>1:
            m1 = deque.pop(m)
            m2 = deque.pop(m)
            ans *= m1 * m2
            cm -= 2
            k -= 2
        elif cp > 0:
            p1 = deque.pop(p)
            ans *= p1
            k -= 1
            cp -= 1
        else:
            
            ans *= -m[2]
            m1 = deque.popleft(m)
            m2 = deque.popleft(m)
            m3 = deque.popleft(m)
            deque.appendleft(m,m1)
            deque.appendleft(m,m2)
            cm -= 1
            k -= 1
        ans %= mod
else:
    m1 = deque.popleft(m)
    m2 = deque.popleft(m)
    m1 = deque.popleft(p)
    m2 = deque.popleft(p)
    deque.append(m,10**10)
    deque.append(p,10**10)
    while k:
        k-=1
        # print(p,m)
        if p[0] < m[0]:
            ans *= deque.popleft(p)
        else:
            ans *= -deque.popleft(m)
        ans %= mod

print(ans)

Submission status: Accepted

Solution code:
MOD = 1000000007
def maxProductSubarrayOfSizeK(A, n, k): 

	A.sort() 

	product = 1

	if (A[n - 1] == 0 and (k & 1)): 
		return 0

	if (A[n - 1] < 0 and (k & 1)): 
	    A.reverse()
	    for i in range(k):
	        product *= A[i]
	        if abs(product) >= MOD:
	            product = product%MOD
	    return product

	i = 0

	j = n - 1

	if (k & 1): 
		product *= A[j]
		product %= MOD
		j-= 1
		k-=1

	k >>= 1

	for itr in range( k) : 

		left_product = A[i] * A[i + 1] 

		right_product = A[j] * A[j - 1] 

		if (left_product > right_product) : 
			product *= left_product 
			product %= MOD
			i += 2
		
		else : 
			product *= right_product
			product %= MOD
			j -= 2

	return product 

n, k = map(int, input().split(' '))
numbers = [int(x) for x in input().split(' ')]
ans = maxProductSubarrayOfSizeK(numbers, n, k)
#print(ans)
print((ans + MOD)%MOD)

Submission status: Accepted

Solution code:
import heapq
 
mod=10**9+7
n,k=map(int,input().split())
arr=list(map(int,input().split()))
q=[]
cnt_plus=0
for i in range(n):
  if arr[i]>0:
    cnt_plus+=1
    heapq.heappush(q,(-arr[i],1))
  elif arr[i]<0:
    heapq.heappush(q,(arr[i],-1))
  else:
    heapq.heappush(q,(0,0))
pick=[]
prev_plus=0
prev_minus=0
cnt=0
for i in range(k):
  tmp,flag=heapq.heappop(q)
  tmp*=-1
  if flag==0:
    print(0)
    exit()
  if flag==1:
    pick.append(tmp)
    prev_plus=tmp
  if flag==-1:
    if cnt==0:
      prev_minus=tmp
      cnt+=1
    else:
      cnt=0
      pick.append(prev_minus)
      pick.append(tmp)
if cnt==0:
  ans=1
  for i in range(k):
    ans*=pick[i]
    ans%=mod
  print(ans%mod)
else:
  cand_plus=0
  cand_minus=0
  while len(q)!=0:
    tmp,flag=heapq.heappop(q)
    tmp*=-1
    if flag==1 and cand_plus==0:
      cand_plus=tmp
    if flag==-1 and cand_minus==0:
      cand_minus=tmp
  if (k%2==1 and cnt_plus==0) or (cand_plus==0 and cand_minus==0):
    if arr.count(0)!=0:
      print(0)
      exit()
    else:
      q=[]
      for i in range(n):
        heapq.heappush(q,abs(arr[i]))
      ans=1
      for _ in range(k):
        ans*=heapq.heappop(q)
        ans%=mod
      print((-ans)%mod)
  else:
    if prev_plus*cand_plus>=prev_minus*cand_minus:
      pick.append(cand_plus)
    else:
      if prev_plus!=0:
        pick.remove(prev_plus)
        pick.append(prev_minus)
        pick.append(cand_minus)
      else:
        pick.append(cand_plus)
    ans=1
    for i in range(k):
      ans*=pick[i]
      ans%=mod
    print(ans%mod)

Submission status: Accepted

Solution code:
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, gcd
from itertools import accumulate, permutations, combinations, product, groupby, combinations_with_replacement
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from bisect import bisect, bisect_left
from heapq import heappush, heappop
from functools import reduce
def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
def ZIP(n): return zip(*(MAP() for _ in range(n)))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10 ** 9 + 7

N, K = MAP()

A = LIST()

plus0 = []
minus = []
zero = []

for a in A:
    if a >= 0:
        plus0.append(a)
    if a == 0:
        zero.append(a)
    if a < 0:
        minus.append(a)

# print(plus0)
# print(minus)
# print(zero)

if (len(minus) == N and K%2 == 1) or (plus0 and minus and N == K and len(minus)%2 == 1):
    # 答えはマイナスなので最小化を目指す
    if (len(minus) == N and K%2 == 1):
        minus.sort(reverse=True)  # 小さい方からKこ
        ans = 1
        for i in range(K):
            ans *= minus[i]
            ans %= mod
    else:
        ans = 1
        for x in minus+plus0:
            ans *= x
            ans %= mod
    print(ans)
else:
    if len(plus0) == N:
        ans = 1
        plus0.sort(reverse=True)
        for i in range(K):
            ans *= plus0[i]
            ans %= mod
        print(ans)
        exit()

    # 答えは0以上なので最大化を目指す
    ans = 1
    cnt = 0
    plus0.sort()
    minus.sort(reverse=True)
    # print(plus0)
    # print(minus)
    while cnt != K:
        if cnt == K-1 or len(minus) <= 1:
            ans *= plus0.pop()
            cnt += 1
        else:
            if not plus0:
                ans *= minus.pop()
                ans *= minus.pop()
                cnt += 2
            elif len(plus0) == 1:
                if plus0[0] > minus[-1]*minus[-2]:
                    ans *= plus0.pop()
                    cnt += 1
                else:
                    ans *= minus.pop()
                    ans *= minus.pop()
                    cnt += 2
            else:
                if plus0[-1]*plus0[-2] > minus[-1]*minus[-2]:
                    ans *= plus0.pop()
                    cnt += 1
                else:
                    ans *= minus.pop()
                    ans *= minus.pop()
                    cnt += 2
        ans %= mod
    print(ans)

Submission status: Accepted

Solution code:
import sys
readline = sys.stdin.buffer.readline
read = sys.stdin.read
from collections import deque
sys.setrecursionlimit(10 ** 8)
INF = float('inf')
MOD = 10 ** 9 + 7

def main():
    n, k = map(int, readline().split())
    A = list(map(int, readline().split()))
    MOD = int(1e9) + 7
    A.sort()
    ans = 1
    if A[n - 1] == 0 and (k & 1):
        ans = 0
    elif A[n - 1] <= 0 and (k & 1):
        for i in range(n - 1, n - k - 1, -1):
            ans = (ans * A[i]) % MOD
    else:
        i = 0
        j = n - 1
        if k & 1:
            ans = (ans * A[j]) % MOD
            j -= 1
            k -= 1
        k >>= 1
        for itr in range(k):
            left_product = A[i] * A[i + 1]
            right_product = A[j] * A[j - 1]
            if left_product > right_product:
                ans = (ans * left_product) % MOD
                i += 2
            else:
                ans = (ans * right_product) % MOD
                j -= 2

    print(ans % MOD)

if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
import sys
input = sys.stdin.readline
mod = 10**9+7

n, k = map(int, input().split())
A = list(map(int, input().split()))
B = []
C = []
s = 0
t = 0
for a in A:
  if a < 0:
    B.append(-a)
    s += 1
  elif a > 0:
    C.append(a)
    t += 1
if s + t < k:
  print(0)
  exit()
if s + t == k:
  if k == n:
    ans = 1
    for a in A:
      ans *= a
      ans %= mod
    print(ans)
  else:
    if s%2:
      print(0)
    else:
      ans = 1
      for b in B:
        ans *= b
        ans %= mod
      for c in C:
        ans *= c
        ans %= mod
      print(ans)
  exit()
B.sort(reverse=True)
C.sort(reverse=True)
ans = 1
nb = 0
nc = 0
if t == 0:
  if k%2:
    if s == n:
      for b in B[-k:]:
        ans *= b
        ans %= mod
      ans *= -1
      ans %= mod
      print(ans)
    else:
      print(0)
  else:
    for b in B[:k]:
      ans *= b
      ans %= mod
    ans %= mod
    print(ans)
  exit()
for _ in range(k):
  if nb >= s:
    ans *= C[nc]
    ans %= mod
    nc += 1
  elif nc >= t:
    ans *= B[nb]
    ans %= mod
    nb += 1
  else:
    if B[nb] > C[nc]:
      ans *= B[nb]
      ans %= mod
      nb += 1
    else:
      ans *= C[nc]
      ans %= mod
      nc += 1
if nb%2:
  if nb == s:
    ans *= pow(B[-1], mod-2, mod)
    ans %= mod
    ans *= C[nc]
    ans %= mod
    print(ans)
  elif nc == t:
    ans *= B[nb]
    ans %= mod
    ans *= pow(C[-1], mod-2, mod)
    ans %= mod
    print(ans)
  else:
    if nc == 0:
      ans *= pow(B[nb-1], mod-2, mod)
      ans %= mod
      ans *= C[0]
      ans %= mod
      print(ans)
    else:
      if C[nc-1]*C[nc] >= B[nb-1]*B[nb]:
        ans *= pow(B[nb-1], mod-2, mod)
        ans %= mod
        ans *= C[nc]
        ans %= mod
        print(ans)
      else:
        ans *= pow(C[nc-1], mod-2, mod)
        ans %= mod
        ans *= B[nb]
        ans %= mod
        print(ans)
else:
  print(ans)

Submission status: Accepted

Solution code:
N,K=list(map(int,input().split()))
a=list(map(int,input().split()))
a.sort(key=lambda x:abs(x),reverse=True)

mod=10**9+7

p=[]
m=[]
zero=False
cntm=0
cntp=0

for aa in a:
    if aa>=0:
        p.append(aa)
        if cntp+cntm<K:
            cntp+=1
    elif aa<0:
        m.append(-aa)
        if cntp+cntm<K:
            cntm+=1
    
    if aa==0:
        zero=True

ans=1

if cntm%2==1:
    if cntm+1<=len(m) and cntm+1<=K and cntp+1<=len(p) and cntp+1<=K:
        if p[cntp]*p[cntp-1]>m[cntm]*m[cntm-1]:
            cntp+=1
            cntm-=1
        else:
            cntm+=1
            cntp-=1
    elif cntm+1<=len(m) and cntm+1<=K:
        cntm+=1
        cntp-=1
    elif cntp+1<=len(p) and cntp+1<=K:
        cntp+=1
        cntm-=1
    else:
        if zero:
            print(0)
            exit(0)
        
        for i in range(K):
            ans*=a[N-i-1]
            ans=(ans+mod*mod)%mod
        
        print(ans)
        exit(0)

for i in range(cntm):
    ans*=m[i]
    ans%=mod
for i in range(cntp):
    ans*=p[i]
    ans%=mod

print(ans)

Submission status: Accepted

Solution code:

import sys
sys.setrecursionlimit(10 ** 7)
input = sys.stdin.readline

n, k = map(int, input().split())
a = list( map(int, input().split()))
p = 10**9+7

a.sort()

from bisect import bisect_left, bisect_right
zerostart = bisect_left(a, 0)
posstart = bisect_right(a, 0)

aneg = a[:zerostart]
cntzero = posstart - zerostart
apos = a[posstart:]

cntneg = len(aneg)
cntpos = len(apos)

# 答えが0になる時
if k > n-cntzero:
    print(0)
    exit()

# 答えが正になる時
if k <= cntpos or (k%2==0 and  k <= (cntneg//2)*2 + cntpos) or (k%2==1 and cntpos%2==1 and k <= (cntneg//2)*2 + cntpos-1):
    pos_pair_mix=[]

    apos.sort(reverse=True)
    for i in range(cntpos//2):
        pos_pair_mix.append((apos[2*i]*apos[2*i+1],+1,2*i))

    for i in range(cntneg//2):
        pos_pair_mix.append((aneg[2*i]*aneg[2*i+1],-1,2*i))

    pos_pair_mix.sort(key=lambda x:x[0],reverse=True)

    ans = 1
    i_last_apos=0

    for i in range(k//2):
        ans*=pos_pair_mix[i][0]%p
        ans%=p
        if pos_pair_mix[i][1]==1:
            i_last_apos = pos_pair_mix[i][2]+2

    if k%2==0:
        print(ans%p)
        exit()
    else:
        print((ans*apos[i_last_apos])%p)
        exit()

# 答えが負になる時
a.sort(key=lambda x:abs(x) )

ans = 1
for i in range(k):
    ans*=a[i]
    ans%=p

print(ans%p)

Submission status: Accepted

Solution code:
N, K = map(int, input().split())
A = list(map(int, input().split()))
MOD = 10 ** 9 + 7

positives = [a for a in A if a > 0]
negatives = [a for a in A if a < 0]
positive_cnt = len(positives)
negative_cnt = len(negatives)
zero_cnt = A.count(0)


if min(2 * (negative_cnt // 2), 2 * (K // 2)) + positive_cnt >= K:
    # 答えが正になる場合
    positives = sorted(positives, reverse=True)
    negatives = sorted(negatives)

    if K % 2 == 1:
        ans = positives[0]
        positives = positives[1:]
        positive_cnt = len(positives)
    else:
        ans = 1

    positives_twin = [positives[2 * i] * positives[2 * i + 1] for i in range(positive_cnt // 2)] + [0]
    negatives_twin = [negatives[2 * i] * negatives[2 * i + 1] for i in range(negative_cnt // 2)] + [0]
    positives_twin.sort()
    negatives_twin.sort()

    for i in range(K // 2):
        if positives_twin[-1] <= negatives_twin[-1]:
            ans *= negatives_twin[-1]
            ans %= MOD
            negatives_twin.pop()
        else:
            ans *= positives_twin[-1]
            ans %= MOD
            positives_twin.pop()

    print(ans % MOD)

elif zero_cnt > 0:
    # 答えが０になる場合
    print(0)
else:
    # 答えが負になる場合
    ans = 1
    A_abs = sorted([abs(a) for a in A])
    for a in A_abs[:K]:
        ans *= a
        ans %= MOD
    ans = -ans % MOD
    print(ans)

Submission status: Accepted

Solution code:
n,k = map(int,input().split())
a = list(map(int,input().split()))
mod = 10**9 +7

if(k==n):
    ans = 1
    for ai in a:
        ans *= ai
        ans %= mod
    print(ans)
    exit()

a_plus = []
a_minus = []
cnt_0 = 0

for ai in a:
    if(ai==0):
        cnt_0 += 1
    elif(ai > 0):
        a_plus.append(ai)
    else:
        a_minus.append(ai)

a_plus.sort(reverse = True)
a_minus.sort()

cnt_p = len(a_plus)
cnt_m = len(a_minus)

if(cnt_p + cnt_m < k):
    print(0)
    exit()

if(cnt_p + cnt_m == k)&(cnt_0>0)&(cnt_m%2==1):
    print(0)
    exit()


if(cnt_m == n)&(k%2==1):
    ans = 1
    for i in range(k):
        ans *= a_minus[cnt_m - 1 - i]
        ans %= mod
    print(ans)
    exit()
elif(cnt_p == 0)&(k%2==1):
    print(0)
    exit()

p_ind = 0
m_ind = 0

ans = 1
if(k%2==1):
    ans = a_plus[0]
    p_ind = 1

for i in range(k//2):
    tmp_p = 0
    tmp_m = 0
    if(p_ind + 2 <= cnt_p ):
        tmp_p = a_plus[p_ind] * a_plus[p_ind+1]

    if(m_ind + 2 <= cnt_m ):
        tmp_m = a_minus[m_ind] * a_minus[m_ind+1]

    if(tmp_p > tmp_m):
        ans *= tmp_p
        p_ind += 2
    else:
        ans *= tmp_m
        m_ind += 2
    ans %= mod


ans %= mod
print(ans)

Submission status: Accepted

Solution code:
N,K = map(int,input().split())
A = list(map(int,input().split()))
mod = 10**9+7
A.sort()
ans = 1
if A[-1]==0 and K&1: print(0);exit()
if A[-1]<0 and K&1:
    for i in range(N-1,N-1-K,-1):
        ans =(ans*A[i])%mod
    print(ans)
    exit()
l,r = 0,N-1
if K&1:
    ans *= A[-1]
    r-=1
    K-=1
p = K//2
for i in range(p):
    lp = A[l]*A[l+1]
    rp = A[r]*A[r-1]
    if lp>rp:
        ans = (ans*lp)%mod
        l += 2
    else:
        ans = (ans*rp)%mod
        r-=2
print(ans%mod)

Submission status: Accepted

Solution code:
# coding: utf-8


def main():
    N, K = map(int, input().split())
    A = list(map(int, input().split()))
    B = sorted(A, key=lambda x: abs(x), reverse=True)
    Bp = [x for x in B if x > 0]
    Bm = [x for x in B if x < 0]
    Bpm = [x for x in B if x != 0]
    Bmm = []
    for i in range(0, len(Bm)-1, 2):
        Bmm.append(Bm[i]*Bm[i+1])

    q = 10**9 + 7

    n_plus, n_zero, n_minus = 0, 0, 0
    for a in A:
        if a > 0:
            n_plus += 1
        elif a < 0:
            n_minus += 1
        else:
            n_zero += 1

    # if K > n_plus + n_minus:
    #     return 0

    # ans != 0
    rest = K
    ans = 1

    if K <= n_plus + n_minus and not ((n_plus == 0 or K == n_plus + n_minus) and (K-n_plus) % 2 == 1):
        # ans > 0
        i, j = 0, 0
        while rest > 0:
            if rest >= 2 and j < len(Bmm):
                if i+1 < len(Bp):
                    if Bmm[j] >= Bp[i] * Bp[i+1]:
                        ans = (ans * (Bmm[j] % q)) % q
                        j += 1
                        rest -= 2
                    else:
                        ans = (ans * Bp[i]) % q
                        i += 1
                        rest -= 1
                elif i < len(Bp):
                    if Bmm[j] >= Bp[i]:
                        ans = (ans * (Bmm[j] % q)) % q
                        j += 1
                        rest -= 2
                    else:
                        ans = (ans * Bp[i]) % q
                        i += 1
                        rest -= 1
                else:
                    ans = (ans * (Bmm[j] % q)) % q
                    j += 1
                    rest -= 2
            else:
                ans = (ans * Bp[i]) % q
                i += 1
                rest -= 1
        return ans
    elif n_zero > 0:
        return 0
    else:
        # ans < 0
        for i in range(K):
            ans = (ans * Bpm[len(Bpm)-1-i]) % q
        return ans

        # i = 0
        # ip = 0
        # im = 0
        # while rest > 0:
        #     if B[i] > 0:
        #         ans = (ans * B[i]) % q
        #         i += 1
        #         ip += 1
        #         rest -= 1
        #     else:  # B[i] < 0
        #         if rest == 1:
        #             i += 1
        #         elif B[i+1] < 0:  # rest >= 2
        #             ans = (ans * (B[i]*B[i+1] % q)) % q
        #             i += 2
        #             im += 2
        #             rest -= 2
        #         else:  # rest >= 2 and B[i+1] > 0
        #             if Bp[ip] * Bp[ip+1] > Bm[im] * Bm[im+1]:
        #                 ans = (ans * (Bp[ip]*Bp[ip+1] % q)) % q


print(main())

Submission status: Accepted

Solution code:
import sys
INF = float('inf')
MOD = 10**9 + 7
N, K = map(int, input().split())
A = list(map(int, input().split()))
ans = 1
is_pos = 0
for ai in A:
    if ai > 0:
        is_pos += 1
if is_pos == 0 and K % 2 == 1:
    sortA = sorted(A, key=abs)    
    for ai in sortA[:K]:
        ans = (ans * ai) % MOD
    print(ans)
    sys.exit()
        
sortA = sorted(A, reverse=True, key=abs)
pos_list = [0]
neg_list = [0]
for ai in sortA[:K]:
    if ai < 0:
        neg_list += [ai]
    elif ai > 0:
        pos_list += [ai]
    else:
        print(0)
        sys.exit()
# first_pos = 0
# first_neg = 0
first_pos = INF
first_neg = INF
for i in range(K, N):
    if sortA[i] > 0 and first_pos == INF:
        first_pos = sortA[i]
    elif sortA[i] < 0 and first_neg == INF:
        first_neg = sortA[i]
len_pos = len(pos_list)
len_neg = len(neg_list)
if len_pos == 1:
    if len_neg % 2 == 1:
        for i in range(1, len_neg):
            ans = (ans * neg_list[i]) % MOD
    else:
        ans = ans * first_pos
        for i in range(1, len_neg-1):
            ans = (ans * neg_list[i]) % MOD
    print(ans)
    sys.exit()
if len_neg % 2 == 1 or K==N:
    for i in range(1, len_pos):
        ans = (ans * pos_list[i]) % MOD
    for i in range(1, len_neg):
        ans = (ans * neg_list[i]) % MOD
    print(ans)
    sys.exit()
# print(first_neg, first_pos)
if first_neg == INF and first_pos == INF:
    print(0)
    sys.exit()
if first_neg == INF:
    ans = (ans * first_pos) % MOD
    for i in range(1, len_pos):
        ans = (ans * pos_list[i]) % MOD
    for i in range(1, len_neg-1):
        ans = (ans * neg_list[i]) % MOD
    print(ans)
    sys.exit()
if first_pos == INF:
    ans = (ans * first_neg) % MOD
    for i in range(1, len_pos-1):
        ans = (ans * pos_list[i]) % MOD
    for i in range(1, len_neg):
        ans = (ans * neg_list[i]) % MOD
    print(ans)
    sys.exit()
pos2 = abs(pos_list[-1] * first_pos)
neg2 = abs(neg_list[-1] * first_neg)
if pos2 > neg2:
    ans = (ans * first_pos) % MOD
    for i in range(1, len_pos):
        ans = (ans * pos_list[i]) % MOD
    for i in range(1, len_neg-1):
        ans = (ans * neg_list[i]) % MOD
else:
    ans = (ans * first_neg) % MOD
    for i in range(1, len_pos-1):
        ans = (ans * pos_list[i]) % MOD
    for i in range(1, len_neg):
        ans = (ans * neg_list[i]) % MOD
print(ans)

Submission status: Accepted

Solution code:
def main(A, n, k):
    MOD = int(1e9) + 7
    A.sort()
    ans = 1
    if A[n - 1] == 0 and (k & 1):
        ans = 0
    elif A[n - 1] <= 0 and (k & 1):
        for i in range(n - 1, n - k - 1, -1):
            ans = (ans*A[i]) % MOD
    else:
        i = 0
        j = n - 1
        if k & 1:
            ans = (ans*A[j]) % MOD
            j -= 1
            k -= 1
        k >>= 1
        for itr in range(k):
            left_product = A[i] * A[i + 1]
            right_product = A[j] * A[j - 1]
            if left_product > right_product:
                ans = (ans*left_product) % MOD
                i += 2
            else:
                ans = (ans*right_product) % MOD
                j -= 2

    print(ans % MOD)


if __name__ == "__main__":
    N, K = map(int, input().split(' '))
    A = list(map(int, input().split(' ')))
    main(A, N, K)