POJ 1258 Agri-Net

http://poj.org/problem?id=1258

裸求最小生成树

这句话好像没什么影响"Physically, they are limited in length to 80 characters, so some lines continue onto others"

#include <iostream>
#include <stdio.h>
#include <string.h>
#include <queue>
#define READ() freopen("in.txt", "r", stdin);
#define MAXV 20007
#define INF 0x3f3f3f3f
using namespace std;

typedef pair<int,int> P;
int N;
struct Edge
{
    int to, cost, next;
    Edge () {}
    Edge(int to, int cost, int next) : to(to), cost(cost), next(next) {}
}edge[MAXV];

int head[MAXV];
int num = 0;

void Add(int from, int to, int cost)
{
    edge[num] = Edge(to, cost, head[from]);
    head[from] = num++;
}

int prim()
{
    int res = 0;
    int dist[MAXV];
    bool use[MAXV];
    priority_queue<P, vector<P>, greater<P> > que;
    fill(dist, dist+MAXV, INF);
    fill(use, use+MAXV, false);
    dist[1] = 0;
    que.push(P(dist[1], 1));
    while (!que.empty())
    {
        P p = que.top();
        que.pop();
        int v = p.second, d = p.first;
        if (!use[v])//**
        {
            res += dist[v];
        }
        use[v]= true;
        if (dist[v] < d) continue;
        int t = head[v];
        while (t != -1)
        {
            Edge e = edge[t];
            if (!use[e.to] && dist[e.to] > e.cost)//**
            {
                dist[e.to] = e.cost;
                que.push(P(dist[e.to], e.to));
            }
            t = e.next;
        }
    }
    return res;
}


int main()
{
    READ()
    while(~scanf("%d", &N))
    {
        int cost;
        num = 0;
        memset(head, -1, sizeof(head));
        memset(edge, -1, sizeof(edge));
        for (int i = 1; i <= N ;i ++)
        {
            for (int j = 1; j <= N; j++)
            {
                scanf("%d", &cost);
                if (i == j) continue;
                Add(i, j, cost);
                Add(j, i, cost);
            }
        }
        int ans = prim();
        cout << ans << endl;
    }

}