最小生成树 poj 1258

这题很裸，没啥意思，就是今晚被保安吓到了，想来找找水题切切，刚好后面习题还没写。。。刚好写个kruskal压压惊吧。。

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;
#define M 10900 //100*99/2
typedef long long ll;
typedef struct
{
    int from;
    int to;
    int weight;
}edge;
edge e[M];
int n,k;
int p[M];
bool cmp(edge a ,edge b)
{
    return a.weight < b.weight;
}
int find(int x)
{
    return x==p[x]?x:p[x] = find(p[x]);
}
ll kruskal()
{
    for(int i = 0;i < n;i++) p[i] = i;
    ll ans = 0;
    for(int i = 0;i < k;i++)
    {
        int x = find(e[i].from);
        int y = find(e[i].to);
        if(x != y)
        {
            p[x] = y;
            ans += (ll)e[i].weight;
        }
    }
    return ans;
}
int main()
{
    while(scanf("%d",&n)==1)
    {
        k = 0;
        for(int i = 0;i < n;i++)
        {
            for(int j = 0;j < n;j++)
            {
                int temp;
                scanf("%d",&temp);
                if(j > i)
                {
                    e[k].from = i;
                    e[k].to = j;
                    e[k++].weight = temp;
                }
            }
        }
        sort(e,e+k,cmp);
        printf("%lld\n",kruskal());
    }
    return 0;
}