prim-普里姆 poj 1287 示例 [ 实现用到并查集 ]

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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;}