UVa 11747 Heavy Cycle Edges(最小生成树)

来源：互联网发布：qt编程入门视频教程编辑：程序博客网时间：2024/06/05 00:56

题意：给一个图，按照找最小生成树的方法，找到环并输出环中其中最大的边。

思路：一样是用Kruskal算法，只不过加边的时候，判断边上两点在不在一个连通集合中，如果在，则说明加上边得到了环，输出这条边。

#include <algorithm>#include <iostream>#include <sstream>#include <cstring>#include <cstdio>#include <vector>#include <string>#include <queue>#include <stack>#include <cmath>#include <set>#include <map>using namespace std;typedef long long LL;#define mem(a, n) memset(a, n, sizeof(a))#define ALL(v) v.begin(), v.end()#define si(a) scanf("%d", &a)#define sii(a, b) scanf("%d%d", &a, &b)#define siii(a, b, c) scanf("%d%d%d", &a, &b, &c)#define pb push_back#define eps 1e-8const int inf = 0x3f3f3f3f, N = 1e3 + 5, M = 3e4 + 5, MOD = 1e9 + 7;int T, cas = 0;int n, m;int fa[N];struct edge {int u, v, w;edge() {}edge(int u, int v, int w): u(u), v(v), w(w) {}bool operator<(const edge& rhs) const{return w < rhs.w;}}e[M];int find(int x) {if(x == fa[x]) return x;return fa[x] = find(fa[x]);}void work() {vector<int> ans;for(int i = 0; i < n; i ++) fa[i] = i;for(int i = 0; i < m; i ++) {int u = find(e[i].u), v = find(e[i].v);if(u != v) {fa[v] = u;continue;}ans.pb(e[i].w);}int sz = ans.size();if(sz) {for(int i = 0; i < sz - 1; i ++) printf("%d ", ans[i]);printf("%d\n", ans[sz - 1]);} else puts("forest");}int main(){#ifdef LOCAL    freopen("/Users/apple/input.txt", "r", stdin);//  freopen("/Users/apple/out.txt", "w", stdout);#endif    while(sii(n, m), n + m) {    int u, v, w;    for(int i = 0; i < m; i ++) {    siii(u, v, w);    e[i] = edge(u, v, w);    }     sort(e, e + m);    work();    }        return 0;}

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