poj 1287 Networking

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原题链接：http://poj.org/problem?id=1287

最小生成树kruskal的简单用法，具体实现如下：

#define _CRT_SECURE_NO_WARNINGS#include<stdio.h>#include<stdlib.h>#include<string.h>#define Max_N 5000typedef struct node_t{ int from, to, cost; }edge;edge es[Max_N];int V,E,par[Max_N], rank[Max_N];void init(int n){int i;for (i = 0; i < n; i++){par[i] = i;rank[i] = 0;}}int find(int x){if (x == par[x]) return x;else return par[x] = find(par[x]);}void unite(int x, int y){x = find(x), y = find(y);if (x == y) return;if (rank[x] < rank[y]) par[x] = y;else{par[y] = x;if (rank[x] == rank[y]) rank[x]++;}}int same(int x, int y){return find(x) == find(y);}int cmp(const void *a, const *b){edge t = *(edge *)a, _t = *(edge *)b;return t.cost - _t.cost;}int kruskal(){init(V);qsort(es, E, sizeof(es[0]), cmp);int i, res = 0;for (i = 0; i<E; i++){edge e = es[i];if (!same(e.from, e.to)){unite(e.from, e.to);res += e.cost;}}return res;}int main(){#ifdef LOCALfreopen("input.txt", "r", stdin);freopen("output.txt", "w+", stdout);#endifchar ch;int i,a,b,c;while (EOF != scanf("%d", &V) && 0 != V){scanf("%d", &E);for (i = 0; i < E; i++){scanf("%d %d %d", &a, &b, &c);es[i] = (edge){ --a, --b, c };}printf("%d\n", kruskal());scanf("%c", &ch);}return 0;}

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