HDU_1874 畅通工程续(SPFA)

　　查SPFA的资料时偶尔看到一种运用，然后很淡定的敲之1A了

15MS+328k   code:

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;

const int N = 207;
const int inf = 100000000;

int vis[N], map[N][N];
int dis[N], q[N];

void spfa(int n, int s)
{
    int i, f, r, p;
    memset(vis, 0, sizeof(vis));
    for(i = 0; i < N; i++)
        q[i] = 0;
    for(i = 0; i < n; i++)
        dis[i] = inf;
    dis[s] = 0; vis[s] = 1;
    q[0] = s; f = 0; r = 1;
    while(f < r)
    {
        p = q[f];
        for(i = 0; i < n; i++)
            if(dis[i] > map[p][i] + dis[p])
            {
                dis[i] = map[p][i] + dis[p];
                if(!vis[i])
                {
                    q[r++] = i;
                    vis[i] = 1;
                }
            }
        vis[p] = 0;
        f++;
    }
}

int main()
{
    int n, m, i, j, a, b, c;
    //freopen("data.in", "r", stdin);
    while(~scanf("%d%d", &n, &m))
    {
        for(i = 0; i < n; i++)
            for(j = 0; j < n; j++)
            {
                map[i][j] = inf;
                if(i == j)    map[i][j] = 0;
            }
        while(m--)
        {
            scanf("%d%d%d", &a, &b, &c);
            if(c < map[a][b])
                map[a][b] = map[b][a] = c;
        }
        scanf("%d%d", &a, &b);
        spfa(n, a);
        if(dis[b] < inf)
            printf("%d\n", dis[b]);
        else
            printf("-1\n");
    }
    return 0;
}