POJ 1611 解题报告

来源：互联网发布：卡iphone7plus在线软件编辑：程序博客网时间：2024/05/29 07:23

这道题是union-find的应用，就是找到和0在一个集合的所有元素个数。

1611Accepted372K16MSC++1636B

/* ID: thestor1 LANG: C++ TASK: poj1611 */#include <iostream>#include <fstream>#include <cmath>#include <cstdio>#include <cstring>#include <limits>#include <string>#include <vector>#include <list>#include <set>#include <map>#include <queue>#include <stack>#include <algorithm>#include <cassert>using namespace std;const int MAXN = 30000;void makeset(const int N, std::vector<int> &parent, std::vector<int> &rank){for (int u = 0; u < N; ++u){parent[u] = u;rank[u] = 0;}}int find(int u, std::vector<int> &parent){if (parent[u] != u){parent[u] = find(parent[u], parent);}return parent[u];}void union_set(int u, int v, std::vector<int> &parent, std::vector<int> &rank){int ru = find(u, parent);int rv = find(v, parent);if (ru == rv){return;}if (rank[ru] < rank[rv]){parent[ru] = rv;}else if (rank[rv] < rank[ru]){parent[rv] = ru;}else{parent[ru] = rv;rank[rv]++;}}int main(){std::vector<int> parent(MAXN);std::vector<int> rank(MAXN);int n, m;while (scanf("%d%d", &n, &m) && n != 0){makeset(n, parent, rank);for (int i = 0; i < m; ++i){int k;scanf("%d", &k);if (k == 0){continue;}int u;scanf("%d", &u);for (int j = 1; j < k; ++j){int v;scanf("%d", &v);union_set(u, v, parent, rank);}}int cnt = 1;for (int i = 1; i < n; ++i){if (find(0, parent) == find(i, parent)){cnt++;}}printf("%d\n", cnt);}return 0;  }

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