hdu 2680 Choose the best route 解题报告

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=2680

题目意思：实质就是给定一个多源点到单一终点的最短路。

     卑鄙题～～～有向图。初始化map时 千万不要写成 map[i][j] = map[j][i] = X。

    

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

#define INF 0xfffffff
const int maxn = 1000 + 5;
int dist[maxn], map[maxn][maxn], vis[maxn];
int n, m, s;

void Init()
{
    for (int i = 0; i <= n; i++)
    {
        for (int j = 0; j <= n; j++)
            map[i][j] = (i == j ? 0 : INF);
    }
    int p, q, t, w;
    for (int i = 0; i < m; i++)
    {
        scanf("%d%d%d", &p, &q, &t);
        if (map[p][q] > t)
            map[p][q] = t;   // 写成map[p][q] = map[q][p] = t 会wa的！！！
    }
    scanf("%d", &w);
    for (int i = 0; i < w; i++)
    {
        scanf("%d", &p);
        map[0][p] = map[p][0] = 0;
    }
    for (int i = 0; i <= n; i++)
        dist[i] = map[0][i];
}

void Dijkstra()
{
    int u, maxx;
    memset(vis, 0, sizeof(vis));
    for (int i = 0; i <= n; i++)
    {
        maxx = INF;
        for (int j = 0; j <= n; j++)
        {
            if (!vis[j] && dist[j] < maxx)
                maxx = dist[u=j];
        }
        vis[u] = 1;
        for (int j = 0; j <= n; j++)
        {
            if (dist[j] > dist[u] + map[u][j])
                dist[j] = dist[u] + map[u][j];
        }
    }
}

int main()
{
    while (scanf("%d%d%d", &n, &m, &s) != EOF)
    {
        Init();
        Dijkstra();
        printf("%d
", dist[s] == INF ? -1 : dist[s]);
    }
    return 0;
}