prim-普里姆 poj 1287 示例 [ 实现用到并查集 ]

prim算法 ： 初始化-> 找最小值，更新 - 重复 找 n-1 次。

#include <iostream>
#include <string>
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <cmath>
#include <vector>
#include <stack>
#include <deque>
#include <queue>
#include <bitset>
#include <list>
#include <map>
#include <set>
#include <iterator>
#include <algorithm>
#include <functional>
#include <utility>
#include <sstream>
#include <climits>
#include <cassert>
#define BUG puts("here!!!");

using namespace std;
const int N = 105;
const int INF = 0x7fffffff;
int cost[N][N];
int lowc[N];
bool vis[N];
int n, m;
void prim(int p) {
	memset(vis, false, sizeof(vis));
	memset(lowc, 0, sizeof(lowc));
	for(int i = 1; i <= p; i++) {
		if(cost[1][i] != -1) {
			lowc[i] = cost[1][i];
		}
		else lowc[i] = INF;
	}
	vis[1] = true;
	int sum = 0;
	for(int i = 1; i < p; i++) {
		int mini = INF, c = 0;
		for(int j = 1; j <= p; j++) {
			if(!vis[j] && lowc[j] < mini) {
				mini = lowc[j];
				c = j;
			}
		}
		sum += mini;
		vis[c] = true;
		for(int j = 1; j <= p; j++) {
			if(!vis[j] && cost[c][j] != -1 && cost[c][j] < lowc[j]) {
				lowc[j] = cost[c][j];
			}
		}
	}
	cout << sum << endl;
}
int main() {
	while(cin >> n, n) {
		cin >> m;
		memset(cost, -1, sizeof(cost));
		int a, b, c;
		for(int i = 0; i < m; i++) {
			cin >> a >> b >> c;
			if((cost[a][b] != -1 && c < cost[a][b]) || cost[a][b] == -1) {
				cost[a][b] = cost[b][a] = c;
			}
		}
		prim(n);
	}
	return 0;
}