poj2421 Constructing Roads

題目鏈接：http://poj.org/problem?id=2421
題意：給你一個鄰接矩陣並且還告訴你已經有一些邊相連了，讓你求最小生成樹
解析：已經相連的邊賦值爲0，然後直接做最小生成樹

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;
const int maxn = 1e5+100;
struct node
{
    int u,v,c;
    node () {}
    node (int _u,int _v,int _c)
    {
        u = _u;
        v = _v;
        c = _c;
    }
    bool operator < (const node &b)const
    {
        return c<b.c;
    }
}a[maxn];
int tmp[105][105];
int fa[105];
int getfa(int x)
{
    if(x==fa[x])
        return fa[x];
    return fa[x] = getfa(fa[x]);
}
int main(void)
{
    int n,m;
    scanf("%d",&n);
    for(int i=1;i<=n;i++)
    {
        fa[i] = i;
        for(int j=1;j<=n;j++)
            scanf("%d",&tmp[i][j]);
    }
    scanf("%d",&m);
    while(m--)
    {
        int x,y;
        scanf("%d %d",&x,&y);
        tmp[x][y] = 0;
    }
    int cnt = 0,ans = 0;
    for(int i=1;i<=n;i++)
    {
        for(int j=1;j<=n;j++)
            a[cnt++] = node(i,j,tmp[i][j]);
    }
    sort(a,a+cnt);
    for(int i=0;i<cnt;i++)
    {
        int t1 = getfa(a[i].u);
        int t2 = getfa(a[i].v);
        if(t1!=t2)
        {
            fa[t1] = t2;
            ans += a[i].c;
        }
    }
    printf("%d\n",ans);
    return 0;
}