3 3

0 1 1

0 2 3

1 2 1

0 2

3 1

0 1 1

1 2

2

-1

迪科斯徹的模板題。

#include <stdio.h>

#include <string.h>

#include <algorithm>

#include <math.h>

#include <stack>

#define lson o<<1, l, m

#define rson o<<1|1, m+1, r

using namespace std;

typedef long long LL;

const int maxn = 205;

const int MAX = 0x3f3f3f3f;

const int mod = 1000000007;

int m, n, st, en;

int g[205][205], dij[205], vis[205];

void DIJ() {

    memset(dij, MAX, sizeof(dij));

    memset(vis, 0, sizeof(vis));

    dij[st] = 0;

    for(int i = 0; i < n; i++){

        int tmp = MAX, pos;

        for(int j = 0; j < n; j++)

            if(vis[j] == 0 && dij[j] < tmp) {

                tmp = dij[j];

                pos = j;

            }

        vis[pos] = 1;

        for(int j = 0; j < n; j++)

            if(vis[j] == 0 &&dij[pos] + g[pos][j] < dij[j]) dij[j] = dij[pos] + g[pos][j];

    }

}

int main()

{

    while(~scanf("%d%d", &n, &m)) {

        memset(g, MAX, sizeof(g));

        for(int i = 1; i <= m; i++) {

            int a, b, c;

            scanf("%d%d%d", &a, &b, &c) ;

            if(c > g[a][b]) continue;

            g[a][b] = g[b][a] = c;

        }

        scanf("%d%d", &st, &en);

        DIJ();

        if(vis[en]) printf("%d\n", dij[en]);

        else printf("-1\n");

    }

    return 0;

}