HDU1102：并查集+最小生成树（Kruskal）

HDU1102

题解：已经有了的边就合并，然后剩下的边求最小生成树即可。

代码：

#include <bits/stdc++.h>
using namespace std;
int const N = 200 + 10;
int const M = 10000 + 10;
int n,m,q,a[N][N],fa[N];
struct Edge
{
	int u,v,dist;
	Edge(){}
	Edge(int uu,int vv,int dd):u(uu),v(vv),dist(dd){}
}p[M];
int find(int x){
	return x == fa[x] ? x : (fa[x] = find(fa[x]));
}
bool cmp(Edge a,Edge b){
	return a.dist < b.dist;
}
int Kruskal(){
	int sum = 0,e = 0;
	sort(p+1,p+1+m,cmp);
	for(int i=1;i<=m;i++){
		if(e == n-1)	break;
		int x = find(p[i].u),	y = find(p[i].v);
		if(x != y){
			e++;
			sum += p[i].dist;
			fa[x] = y;
		}
	}
	return sum;
}
int main(){
	while(~scanf("%d",&n)){
		m = 0;
		for(int i=1;i<=n;i++)	fa[i] = i;
		for(int i=1;i<=n;i++)
			for(int j=1;j<=n;j++){
				scanf("%d",&a[i][j]);
				p[++m] = Edge(i,j,a[i][j]);
			}
		scanf("%d",&q);   
		for(int i=0;i<q;i++){
			int x,y;	scanf("%d%d",&x,&y);
			int fx = find(x),	fy = find(y);
			fa[fx] = fy;
		}
		int ans = Kruskal();
		printf("%d\n",ans);
	}
}