Problem:
 Score : 500 points    Problem Statement There are N towns numbered 1 to N and M roads. The i -th road connects Town A_i and Town B_i bidirectionally and has a length of C_i .  Takahashi will travel between these towns by car, passing through these roads. The fuel tank of his car can contain at most L liters of fuel, and one liter of fuel is consumed for each unit distance traveled. When visiting a town while traveling, he can full the tank (or choose not to do so). Travel that results in the tank becoming empty halfway on the road cannot be done.  Process the following Q queries:   The tank is now full. Find the minimum number of times he needs to full his tank while traveling from Town s_i to Town t_i . If Town t_i is unreachable, print -1 .       Constraints  All values in input are integers.  2 \leq N \leq 300  0 \leq M \leq \frac{N(N-1)}{2}  1 \leq L \leq 10^9  1 \leq A_i, B_i \leq N  A_i \neq B_i  \left(A_i, B_i\right) \neq \left(A_j, B_j\right) (if i \neq j )  \left(A_i, B_i\right) \neq \left(B_j, A_j\right) (if i \neq j )  1 \leq C_i \leq 10^9  1 \leq Q \leq N\left(N-1\right)  1 \leq s_i, t_i \leq N  s_i \neq t_i  \left(s_i, t_i\right) \neq \left(s_j, t_j\right) (if i \neq j )         Input Input is given from Standard Input in the following format:  N  M  L  A_1  B_1  C_1  :  A_M  B_M  C_M  Q  s_1  t_1  :  s_Q  t_Q       Output Print Q lines.  The i -th line should contain the minimum number of times the tank needs to be fulled while traveling from Town s_i to Town t_i . If Town t_i is unreachable, the line should contain -1 instead.        Sample Input 1 3 2 5
1 2 3
2 3 3
2
3 2
1 3      Sample Output 1 0
1  To travel from Town 3 to Town 2 , we can use the second road to reach Town 2 without fueling the tank on the way.  To travel from Town 1 to Town 3 , we can first use the first road to get to Town 2 , full the tank, and use the second road to reach Town 3 .       Sample Input 2 4 0 1
1
2 1      Sample Output 2 -1  There may be no road at all.       Sample Input 3 5 4 4
1 2 2
2 3 2
3 4 3
4 5 2
20
2 1
3 1
4 1
5 1
1 2
3 2
4 2
5 2
1 3
2 3
4 3
5 3
1 4
2 4
3 4
5 4
1 5
2 5
3 5
4 5      Sample Output 3 0
0
1
2
0
0
1
2
0
0
0
1
1
1
0
0
2
2
1
0

Solution (Python):
def main():
  import sys
  import numpy as np
  from scipy.sparse import csr_matrix
  from scipy.sparse.csgraph import floyd_warshall as f
  t=np.fromstring(sys.stdin.buffer.read(),'i',sep=' ')
  n,m,l=t[:3]
  m=m*3+3
  print('\n'.join((f(f(csr_matrix((t[5:m:3],(t[3:m:3],t[4:m:3])),[n+1]*2),0)<=l)[t[m+1::2],t[m+2::2]].clip(0,n).astype(int)%n-1).astype(str).tolist()))
main()

Solution (Python):
def main():
  import sys
  import numpy as np
  from scipy.sparse import csr_matrix
  from scipy.sparse.csgraph import floyd_warshall
  t=np.fromstring(sys.stdin.buffer.read(),'i',sep=' ')
  n,m,l=t[:3]
  t=t[3:]
  m*=3
  print('\n'.join((floyd_warshall(floyd_warshall(csr_matrix((t[2:m:3],(t[:m:3],t[1:m:3])),[n+1]*2),0)<=l)[t[m+1::2],t[m+2::2]].clip(0,n).astype(int)%n-1).astype(str).tolist()))
main()

Solution (Python):
def main():
  import sys
  import numpy as np
  from scipy.sparse import csr_matrix
  from scipy.sparse.csgraph import floyd_warshall
  t=np.fromstring(sys.stdin.buffer.read(),'i',sep=' ')
  n,m,l=t[:3]
  t=t[3:]
  m*=3
  print('\n'.join(map(str,map(int,floyd_warshall(floyd_warshall(csr_matrix((t[2:m:3],(t[:m:3],t[1:m:3])),[n+1]*2),0)<=l)[t[m+1::2],t[m+2::2]].clip(0,n)%n-1))))
main()

Solution (Python):
n,m,l=map(int,input().split())
INF=1001001001
dist=[[INF for i in range(n)] for j in range(n)]
dist2=[[INF for i in range(n)] for j in range(n)]
for i in range(n):
  dist[i][i]=0
  dist2[i][i]=0
for i in range(m):
  a,b,c=map(int,input().split())
  a-=1
  b-=1
  dist[a][b]=c
  dist[b][a]=c

for k in range(n):
  for i in range(n):
    for j in range(n):
      dist[i][j]=min(dist[i][j],dist[i][k]+dist[k][j])
for i in range(n):
  for j in range(n):
    if dist[i][j]<=l:
      dist2[i][j]=1

for k in range(n):
  for i in range(n):
    for j in range(n):
      dist2[i][j]=min(dist2[i][j],dist2[i][k]+dist2[k][j])

q=int(input())
for i in range(q):
  s,t=map(int,input().split())
  if dist2[s-1][t-1]==INF:
    print(-1)
  else:
    print(dist2[s-1][t-1]-1)

Solution (Python):
from scipy.sparse.csgraph import csgraph_from_dense
from scipy.sparse import csr_matrix
from scipy.sparse.csgraph import floyd_warshall
import numpy as np
N,M,L=map(int,input().split())
A=[0]*M
B=[0]*M
C=[0]*M
for i in range(M):
    A[i],B[i],C[i] = map(int,input().split())
    A[i] -=1
    B[i] -=1
Q=int(input())
ST=[list(map(int,input().split())) for _ in range(Q)]


G = csr_matrix((C, (A, B)), shape=(N, N))
d = floyd_warshall(G, directed=False)
G=np.full((N,N), np.inf)
G[d<=L]=1
G = csr_matrix(G)
E = floyd_warshall(G, directed=False)

for s,t in ST:
    if E[s-1][t-1]==float('inf'):
        print(-1)
    else:
        print(int(E[s-1][t-1]-1))

Solution (Python):

from scipy.sparse.csgraph import floyd_warshall

N,M,L=map(int, input().split())
RG=[[0 for i in range(N)] for j in range(N)]

for i in range(M):
    f,t,c = map(int, input().split())
    if c <= L:
        RG[f-1][t-1] = c
        RG[t-1][f-1] = c

Rd = floyd_warshall(RG, directed=False)

FG=[[0 for i in range(N)] for j in range(N)]
for i in range(N):
    for j in range(i+1, N):
        if Rd[i][j] <= L:
            FG[i][j] = 1
            FG[j][i] = 1

Fd = floyd_warshall(FG, directed=False)

Q=int(input())
for i in range(Q):
    s, t = map(int, input().split())
    v = Fd[s-1][t-1]
    if s == t:
        print (str(0))
    if v == float('inf'):
        print (str(-1))
    else:
        print (str(int(v-1)))

Solution (Python):
from scipy.sparse.csgraph import floyd_warshall as fw

N, M, L = map(int, input().split())

S = [[float("inf") for i in range(N)] for i in range(N)]

for i in range(M):
    a, b, c = map(int, input().split())
    S[a-1][b-1] = c
    S[b-1][a-1] = c

Sdist = fw(S)

Ssup_init = [[float("inf") for i in range(N)] for i in range(N)]

for i in range(N):
    for j in range(N):
        if Sdist[i][j]<=L:
            Ssup_init[i][j] = 1

Ssup = fw(Ssup_init)

Q = int(input())

for i in range(Q):
    s, t = map(int, input().split())
    if Ssup[s-1][t-1]==float("inf"):
        print(-1)
    else:
        print(int(Ssup[s-1][t-1]-1))

Solution (Python):

from scipy.sparse.csgraph import floyd_warshall as fw
N, M, L = map(int, input().split())


S = [[float("INF") for i in range(N)] for i in range(N)]


for i in range(M):
    a, b, c = map(int,input().split())
    S[a-1][b-1] = c
    S[b-1][a-1] = c



Sf = fw(S)

T = [[float("INF")for i in range(N)] for i in range(N)]



for i in range(N):
    for j in range(N):
        if Sf[i][j] <= L:
            T[i][j] = 1




Tf = fw(T)

for i in range(int(input())):
    a, b = map(int, input().split())
    if Tf[a-1][b-1] != float("INF"):
        print(int(Tf[a-1][b-1])-1)
    else:
        print(-1)

Solution (Python):
def w(d):
    n=len(d)
    for k in range(n):
        for i in range(n):
            for j in range(n):
                d[i][j]=min(d[i][j],d[i][k]+d[k][j])
    return d
N,M,L = map(int, input().split())
inf=float('inf')
fuel=[[inf]*N for _ in range(N)]
for i in range(N):
    fuel[i][i]=0
for _ in range(M):
    a,b,c=map(int,input().split())
    fuel[a-1][b-1]=fuel[b-1][a-1]=c
Q=int(input())
ST=[list(map(int, input().split())) for _ in range(Q)]
fuel = w(fuel)
for i in range(N):
    for j in range(N):
        if 0 < fuel[i][j] <= L:
            fuel[i][j]=1
        elif fuel[i][j] != 0:
            fuel[i][j] = inf
fuel = w(fuel)
for st in ST:
    print(fuel[st[0]-1][st[1]-1]-1 if fuel[st[0]-1][st[1]-1] != inf else -1)

Solution (Python):
def warshal(d):
    n=len(d)
    for k in range(1,n):
        for i in range(1,n):
            for j in range(1,n):
                d[i][j]=min(d[i][j],d[i][k]+d[k][j])
    return d
n,m,l=map(int,input().split())
abc=[list(map(int,input().split())) for i in range(m)]
q=int(input())
st=[list(map(int,input().split())) for i in range(q)]
inf=float("inf")
dp=[[inf]*(n+1) for i in range(n+1)]
for i in range(1,n+1):
    dp[i][i]=0
for u in abc:
    a,b,c=u
    dp[a][b]=c
    dp[b][a]=c
dp=warshal(dp)
data=[[inf]*(n+1) for i in range(n+1)]
for i in range(1,n+1):
    for j in range(1,n+1):
        if 0<dp[i][j]<=l:
            data[i][j]=1
        elif dp[i][j]==0:
            data[i][j]=0
data=warshal(data)
for u in st:
    s,t=u
    if data[s][t]!=inf:
        print(data[s][t]-1)
    else:
        print(-1)

Solution (Python):
import sys

N,M,L=map(int, sys.stdin.readline().split())

d=[  [ float("inf") for j in range(N+1) ]  for i in range(N+1) ]

for _ in range(M):
    a,b,c=map(int, sys.stdin.readline().split())
    d[a][b]=c
    d[b][a]=c
    d[a][a]=0
    d[b][b]=0

for k in range(1,N+1):
	for i in range(1,N+1):
		for j in range(1,N+1):
			d[i][j]=min(d[i][j], d[i][k]+d[k][j])

e=[  [ float("inf") for j in range(N+1) ]  for i in range(N+1) ]
for i in range(1,N+1):
    for j in range(i,N+1):
        if i==j:
            e[i][j]=0
            e[j][i]=0
        elif d[i][j]<=L:
            e[i][j]=1
            e[j][i]=1

for k in range(1,N+1):
	for i in range(1,N+1):
		for j in range(1,N+1):
			e[i][j]=min(e[i][j], e[i][k]+e[k][j])


Q=input()
for _ in range(Q):
    s,t=map(int, sys.stdin.readline().split())
    if e[s][t]==float("inf"):
        print -1
    else:
        print e[s][t]-1

Solution (Python):
from scipy.sparse.csgraph import floyd_warshall

N, M, L = map(int, input().split())
INF = 10**9 + 1
dist = [[0 if i == j else INF for i in range(N+1)] for j in range(N+1)]
for i in range(M):
  a, b, c = map(int, input().split())
  dist[a][b] = c
  dist[b][a] = c

dist = floyd_warshall(dist)

dist_2 = [[INF for i in range(N+1)] for j in range(N+1)]
for i in range(1, N+1):
  for j in range(i+1, N+1):
    if dist[i][j] <= L:
      dist_2[i][j] = 1
      dist_2[j][i] = 1

dist_2 = floyd_warshall(dist_2)

Q = int(input())
for i in range(Q):
  s, t = map(int, input().split())
  print(-1 if dist_2[s][t] == INF else int(dist_2[s][t]-1))

Solution (Python):
import sys
input = sys.stdin.readline

def warshall_floyd(d):
    for k in range(N):
        for i in range(N):
            for j in range(N):
                d[i][j] = min(d[i][j], d[i][k] + d[k][j])
    return d


N, M, L = map(int, input().split())
INF = 10 ** 10
d = [[INF for _ in range(N)] for _ in range(N)]
D = [[INF for _ in range(N)] for _ in range(N)]

for i in range(N):
    d[i][i] = 0
for i in range(M):
    A, B, C = map(int, input().split())
    A -= 1
    B -= 1
    d[A][B] = C
    d[B][A] = C
d = warshall_floyd(d)

for i in range(N):
    for j in range(N):
        if 0 < d[i][j] <= L:
            D[i][j] = 1
        elif d[i][j] == 0:
            D[i][j] = 0
D = warshall_floyd(D)

Q = int(input())
for _ in range(Q):
    s, t = map(int, input().split())
    s -= 1
    t -= 1
    print(D[s][t] - 1 if D[s][t] != INF else -1)

Solution (Python):
import sys
input = sys.stdin.readline
N,M,L = map(int, input().split())
INF = float("inf")
dist1 = [[INF]*N for i in range(N)]
dist2 = [[INF]*N for i in range(N)]

for i in range(M):
  A,B,C = map(int, input().split())
  A -= 1
  B -= 1
  dist1[A][B] = C
  dist1[B][A] = C

for i in range(N):
  dist1[i][i] = 0
  dist2[i][i] = 0
  
for k in range(N):
  for i in range(N):
    for j in range(N):
      d = dist1[i][k]+dist1[k][j]
      if dist1[i][j] <= d:
        continue
      dist1[i][j] = d
for i in range(N):
  for j in range(N):
    if dist1[i][j] > L or i==j:
      continue
    dist2[i][j] = 1
  
for k in range(N):
  for i in range(N):
    for j in range(N):
      d = dist2[i][k]+dist2[k][j]
      if dist2[i][j] <= d:
        continue
      dist2[i][j] = d
Q = int(input())
for i in range(Q):
  s,t = map(int, input().split())
  print(dist2[s-1][t-1]-1 if dist2[s-1][t-1]<=L else -1)