思想
- 遍历所有V，考虑让每个顶点介入每个路径，以更新路径
题目
代码
#include <bits/stdc++.h>
using namespace std;
const int N = 210;
const int inf = 0x3f3f3f3f;
int g[N][N];
int n, m, k;
void floyd()
{
for(int t = 1; t <= n; t++)
{
for(int i = 1; i <= n; i++)
{
for(int j = 1; j <= n; j++)
{
g[i][j] = min(g[i][j], g[i][t] + g[t][j]);
}
}
}
}
int main()
{
cin >> n >> m >> k;
for(int i = 1; i <= n; i++)
{
for(int j = 1; j <= n; j++)
{
if(i == j) g[i][j] = 0;
else g[i][j] = inf;
}
}
for(int i = 1; i <= m; i++)
{
int a, b, c;
cin >> a >> b >> c;
g[a][b] = min(g[a][b], c);
}
floyd();
while(k--)
{
int a, b;
cin >> a >> b;
if(g[a][b] > inf / 2) cout << "impossible\n" ;
else cout << g[a][b] << '\n';
}
}
