多源最短路径

#include <bits/stdc++.h>
using namespace std;
#define inf 999999999
int a[102][102];
int main()
{
    int n, m, x,y,z,i,j;
    while(~scanf("%d%d",&n,&m))
    {
        for(i = 1; i<=n; i++)// 初始化数组
        {
            for(j = 1; j <=n; j++)
            {
                if(i == j)
                {
                    a[i][j] = 0;
                }
                else a[i][j] = inf;
            }
        }
        for(i = 1; i<=m; i++)
        {
            cin>>x>>y>>z;
            a[x][y] = a[y][x] = min(a[x][y], z);
        }
        for(int k = 1; k<=n; k++)//算法核心代码
        {
            for(i = 1; i<=n; i++)
            {
                for(j = 1; j <=n; j++)
                {
                    if(a[i][j]>a[i][k]+a[k][j])
                        a[i][j] = a[i][k]+a[k][j];
                }
            }
        }
        printf("%d\n",a[1][n]);
    }
}