最短路 || POJ 2387 Til the Cows Come Home

从点N到1的最短路

*记得无向图两个方向都要建边就好了……

以及多组数据= =

#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>
using namespace std;
#define SZ 4005
#define INF 1e9+10
int head[SZ],nxt[SZ],tot = 0;
struct edge
{
    int t,d;
}l[SZ];
void build(int f,int t,int d)
{
    l[++tot] = (edge){t,d};
    nxt[tot] = head[f];
    head[f] = tot;
}
queue<int> q;
bool use[SZ];
int dist[SZ];
int spfa(int s, int e)
{
    memset(dist, 63, sizeof(dist));
    memset(use, 0, sizeof(use));
    use[s] = 1;
    dist[s] = 0;
    q.push(s);
    while(!q.empty())
    {
        int u = q.front(); q.pop();
        use[u] = 0;
        for(int i = head[u];i;i = nxt[i])
        {
            int v = l[i].t;
            if(dist[v] > dist[u] + l[i].d)
            {
                dist[v] = dist[u] + l[i].d;
                if(!use[v])
                    use[v] = 1, q.push(v);
            }
        }
    }
    return dist[e];
}
int main()
{
    int T, N;
    while(scanf("%d %d", &T, &N) != EOF)
    {
        memset(head, 0, sizeof(head));
        tot = 0;
        for(int i = 0; i < T; i++)
        {
            int x, y, z;
            scanf("%d %d %d", &x, &y, &z);
            build(x, y, z);
            build(y, x, z);
        }
        printf("%d
", spfa(N, 1));
    }
    return 0;
}