Hdu 1102 Constructing Roads

简单的最小生成树问题，关键在于建图的正确性。

CODE：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <algorithm>
using namespace std;

const int SIZE = 110;

struct node
{
    int u, v, w;
    
}edge[SIZE*SIZE];

int p[SIZE];

int find(int x)
{
    return p[x] == x? x : p[x] = find(p[x]);
}

int cmp(const node a, const node b)
{
    return a.w <= b.w;
}

int Kruskal(int n, int m)
{
    int ans = 0;
    sort(edge, edge+m, cmp);
    for(int i = 0; i < m; i++)
    {
        int x = find(edge[i].u);
        int y = find(edge[i].v);
        if(x != y)
        {
            ans += edge[i].w;
            p[x] = y;
        }
    }
    return ans;
}


int main()
{
    int n, m, t;
    int k;
    int i, j;
    int a, b, c;
    while(~scanf("%d", &n))
    {
        m = 0;
        for(i = 1; i <= n; i++)
        {
            for(j = 1; j <= n; j++)
            {
                scanf("%d", &c);
                if(i <= j) continue;
                edge[m].v = i;
                edge[m].u = j;
                edge[m].w = c;
                m++;
            }
        }
        for(i = 1; i <= n; i++) p[i] = i;
        scanf("%d", &t);
        while(t--)
        {
            scanf("%d%d", &a, &b);
            i = find(a);
            j = find(b);
            p[i] = j;
        }
        printf("%d\n", Kruskal(n, m));
    }

}