（最短路 SPFA）Invitation Cards -- poj -- 1511

链接：

http://poj.org/problem?id=1511

http://acm.hust.edu.cn/vjudge/contest/view.action?cid=82829#problem/J

代码：

#include <iostream>
#include <cstring>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <vector>
#include <queue>
#include <map>
using namespace std;

#define N 1000005
#define oo 0x3fffffff

struct node
{
    int a, b, next;
    long long p;
}s1[N], s[N];

int n, m, head[N];
long long dis[N];
bool vis[N];

void Add(int a, int b, long long p, int k)
{
    s1[k].a=a;
    s1[k].b=b;
    s1[k].p=p;
    s1[k].next=head[a];
    head[a]=k;
}

long long spfa()
{
    queue<int>Q;
    Q.push(1);
    vis[1]=true;

    for(int i=1; i<=n; i++)
        dis[i]=oo;
    dis[1]=0;

    while(Q.size())
    {
        int i = Q.front(); Q.pop();
        vis[i] = false;

        for(int j=head[i]; j != 0; j = s1[j].next)
        {
            int a = s1[j].a, b = s1[j].b;
            int p = s1[j].p;

            if(dis[a]+p < dis[b])
            {
                dis[b] = dis[a] + p;

                if(vis[b] == false)
                {
                    Q.push(b);
                    vis[b] = true;
                }
            }
        }
    }

    long long sum=0;

    for(int i=1; i<=n; i++)
        sum += dis[i];
    return sum;
}

int main()
{
    int t;
    scanf("%d", &t);
    while(t--)
    {
        scanf("%d%d", &n, &m);

        int i;

        memset(head, 0, sizeof(head));
        memset(s, 0, sizeof(s));
        memset(s1, 0, sizeof(s1));

        for(i=1; i<=m; i++)
        {
            scanf("%d%d%I64d", &s[i].a, &s[i].b, &s[i].p);
            Add(s[i].a, s[i].b, s[i].p, i);
        }

        long long ans = spfa();

        memset(head, 0, sizeof(head));
        for(i=1; i<=m; i++)
            Add(s[i].b, s[i].a, s[i].p, i);

        ans += spfa();
        printf("%I64d
", ans);
    }
    return 0;
}