poj2421 MST（prim+临接表）

最小生成树水题，写一个试试ubuntu下的nsight好用否！

将已经建好的路的权值赋为0就OK,然后用prim算法构建最小生成树。

#include <stdio.h>
#include <string.h>
#define N 101
#define INF 0x3fffffff
int first[N],visited[N],dis[N],top,n;
struct edge{
	int y,w,next;
}e[N*N];
void add(int x,int y,int w){
	e[top].y = y;
	e[top].w = w;
	e[top].next = first[x];
	first[x] = top++;
}
void update(int x,int y){
	int i;
	for(i = first[x];i!=-1;i=e[i].next)
		if(e[i].y == y){
			e[i].w = 0;
			return;
		}
}
void init(){
	int i;
	memset(first,-1,sizeof(first));
	memset(visited,0,sizeof(visited));
	top = 0;
	for(i = 0;i<=n;i++)
		dis[i] = INF;
}
int prim(){
	int i,j,pos,min,res = 0;
	for(i = first[1];i!=-1;i=e[i].next)
		dis[e[i].y] = e[i].w;
	pos = 1;
	visited[1] = 1;
	for(i = 1;i<n;i++){
		min = INF;
		for(j = 1;j<=n;j++)
			if(!visited[j] && dis[j]<min){
				pos = j;
				min = dis[j];
			}
		visited[pos] = 1;
		res += min;
		for(j = first[pos];j!=-1;j=e[j].next)
			if(!visited[e[j].y] && dis[e[j].y]>e[j].w)
				dis[e[j].y] = e[j].w;
	}
	return res;
}
int main(){
	//freopen("a.txt","r",stdin);
	while(scanf("%d",&n)!=EOF){
		int i,j,w,num;
		init();
		for(i = 1;i<=n;i++)
			for(j = 1;j<=n;j++){
				scanf("%d",&w);
				if(i!=j)
					add(i,j,w);
			}
		scanf("%d",&num);
		while(num--){
			scanf("%d %d",&i,&j);
			update(i,j);update(j,i);
		}
		printf("%d\n",prim());
	}
	return 0;
}