Problem: There is a staircase with N steps. Takahashi is now standing at the foot of the stairs, that is, on the 0-th step. He can climb up one or two steps at a time.  However, the treads of the a_1-th, a_2-th, a_3-th, \ldots, a_M-th steps are broken, so it is dangerous to set foot on those steps.  How many are there to climb up to the top step, that is, the N-th step, without setting foot on the broken steps? Find the count modulo 1\ 000\ 000\ 007.

Submission attempts (in order):
import sys
import math
import itertools
import bisect
from copy import copy
from collections import deque,Counter
from decimal import Decimal
def s(): return input()
def k(): return int(input())
def S(): return input().split()
def I(): return map(int,input().split())
def X(): return list(input())
def L(): return list(input().split())
def l(): return list(map(int,input().split()))
def lcm(a,b): return a*b//math.gcd(a,b)
def gcd(*numbers): reduce(math.gcd, numbers)
sys.setrecursionlimit(10 ** 9)
mod = 10**9+7
count = 0
ans = 0
inf = float("inf")

def dpp(n):
    for i in range(2,n+1):
        if a[i] = 0:
            dp[i] = 0
        else:
            dp[i] = dp[i-1]+dp[i-2]
    return dp[n]

N,M = I()
a = [1]*(N +1)
for i in range(M):
    x = k()
    a[x] = 0

dp = [0]*(N+1)
if 1 in a:
    dp[1] = 0
    dp[0] = 1
else:
    dp[0] = dp[1] =1

print(dpp(N) % mod)


import sys
import math
import itertools
import bisect
from copy import copy
from collections import deque,Counter
from decimal import Decimal
def s(): return input()
def k(): return int(input())
def S(): return input().split()
def I(): return map(int,input().split())
def X(): return list(input())
def L(): return list(input().split())
def l(): return list(map(int,input().split()))
def lcm(a,b): return a*b//math.gcd(a,b)
def gcd(*numbers): reduce(math.gcd, numbers)
sys.setrecursionlimit(10 ** 9)
mod = 10**9+7
count = 0
ans = 0
inf = float("inf")

def dpp(n):
    
    dp = [0]*(N+1)
    dp[0] = 1

    if n == 0:
        return 0
    if n == 1:
        if 1 in a:
            dp[1] = 0
            return 0
        else:
            dp[1] = 1
            return 1

    for i in range(2,n+1):
        if i in a:
            dp[i] = 0
        else:
            dp[i] = dp[i-1]+dp[i-2]
    return dp[n]

N,M = I()
a = []
for i in range(M):
    x = k()
    a.append(x)

print(dpp(N) % mod)


import sys
import math
import itertools
import bisect
from copy import copy
from collections import deque,Counter
from decimal import Decimal
def s(): return input()
def k(): return int(input())
def S(): return input().split()
def I(): return map(int,input().split())
def X(): return list(input())
def L(): return list(input().split())
def l(): return list(map(int,input().split()))
def lcm(a,b): return a*b//math.gcd(a,b)
def gcd(*numbers): reduce(math.gcd, numbers)
sys.setrecursionlimit(10 ** 9)
mod = 10**9+7
count = 0
ans = 0
inf = float("inf")

def dpp(n):
    for i in range(2,n+1):
        if a[i] == 0:
            dp[i] = 0
        else:
            dp[i] = dp[i-1]+dp[i-2]
    return dp[n]

N,M = I()
a = [1]*(N +1)
for i in range(M):
    x = k()
    a[x] = 0

dp = [0]*(N+1)
if a[1] == 0:
    dp[1] = 0
    dp[0] = 1
else:
    dp[0] = dp[1] =1

print(dpp(N) % mod)


Verdicts: Runtime Error

Wrong Answer

Accepted