HDOJ 1874 畅通工程续

单源最短路径，Dijkstra，参考白书的写法；

注意INF不能定义为0x7fffffff，因为后面相加可能会溢出，题目中距离最大为10000；

这道题的变态之处在于有重边，遇到重边时需要更新w[i, j]和w[j, i]，WA多次，15ms。

# include <stdio.h>

# include <string.h>



# define INF 0x10ffffff



int main()

{

    int k, i, j, n, m, s, t;

    char v[201];

    int x, d[201], w[201][201];

        

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

    {

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

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

            w[i][j] = INF;

        for (k = 0; k < m; ++k)

        {

            scanf("%d%d%d", &i, &j, &x);

            if (w[i][j] > x) w[j][i] = w[i][j] = x;

           }

        scanf("%d%d", &s, &t);

        if (s == t) {puts("0"); continue;}

        

        memset(v, 0, sizeof(v));

        for (k = 0; k < n; ++k) d[k] = INF;

        d[s] = 0;

        for (k = 0; k < n; ++k)

        {

            x = INF;

            for (j = 0; j < n; ++j) if (!v[j] && d[j]<=x) x = d[i=j];

            v[i] = 1;

            for (j = 0; j < n; ++j) if (d[j] > (m=d[i]+w[i][j])) d[j] = m;

        }

        

        if (d[t] < INF) printf("%d\n", d[t]);

        else puts("-1");

    }

    

    return 0;

}