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链接 :http://acm.hust.edu.cn/vjudge/problem/viewProblem.action?id=34798
给N个点的无向图并且联通,问删除每次一个点之后还剩多少联通分量。
找割顶 如果删除的是割顶 联通分量就会增加,否则还是1(因为原图是联通图),删除割顶之后 联通块的数目 就要看该割顶在几个双联通分量里出现过。
#pragma comment(linker, "/STACK:10240000,10240000") #include <algorithm> #include <iostream> #include <sstream> #include <cstring> #include <cstdlib> #include <cstdio> #include <vector> #include <cmath> #include <queue> #include <stack> #include <set> #include <map> #define mod 4294967296 #define MAX 0x3f3f3f3f #define lson o<<1, l, m #define rson o<<1|1, m+1, r #define SZ(x) ((int)ans.size()) #define MAKE make_pair #define INFL 0x3f3f3f3f3f3f3f3fLL #define mem(a) memset(a, 0, sizeof(a)) const double pi = acos(-1.0); const double eps = 1e-9; const int N = 10005; const int M = 20005; typedef long long ll; using namespace std; int n, m; int pre[N], iscut[N], bcc[N], dfs_clock, bcc_cnt; vector <int> G[N], BCC[N]; struct Edge { int u, v; }; stack <Edge> S; struct C { int id, num; } out[N]; int dfs(int u, int fa) { int lowu = pre[u] = ++dfs_clock; int child = 0; for(int i = 0; i < G[u].size(); i++) { int v = G[u][i]; Edge e = (Edge) {u, v}; if(pre[v] == 0) { S.push(e); child++; int lowv = dfs(v, u); lowu = min(lowu, lowv); if(lowv >= pre[u]) { iscut[u] = 1; bcc_cnt++; BCC[bcc_cnt].clear(); for(;;) { Edge x = S.top(); S.pop(); if(bcc[x.u] != bcc_cnt) { BCC[bcc_cnt].push_back(x.u); bcc[x.u] = bcc_cnt; } if(bcc[x.v] != bcc_cnt) { BCC[bcc_cnt].push_back(x.v); bcc[x.v] = bcc_cnt; } if(x.u == u && x.v == v) break; } } } else if(pre[v] < pre[u] && v != fa) { S.push(e); lowu = min(lowu, pre[v]); } } if(fa < 0 && child == 1) { iscut[u] = 0; } return lowu; } void find_bcc() { mem(pre); mem(iscut); mem(bcc); //mem(ans); dfs_clock = bcc_cnt = 0; for(int i = 0; i < n; i++) { if(pre[i] == 0) dfs(i, -1); } } bool cmp(C x, C y) { if(x.num != y.num) return x.num > y.num; return x.id < y.id; } int ans[N]; int main() { //freopen("in.txt","r",stdin); while(cin >> n >> m && n + m) { int x, y; mem(ans); for(int i = 0; i < n; i++) { G[i].clear(); } while(scanf("%d%d", &x, &y) && x != -1) { G[x].push_back(y); G[y].push_back(x); } find_bcc(); for(int i = 1; i <= bcc_cnt; i++) { for(int j = 0; j < BCC[i].size(); j++) { ans[ BCC[i][j] ] ++; } } int k = 0; for(int i = 0; i < n; i++) { out[i].id = i; if(iscut[i]) { out[i].num = ans[i]; } else { out[i].num = 1; } } sort(out, out + n, cmp); for(int i = 0; i < m; i++) { printf("%d %d\n", out[i].id, out[i].num); } puts(""); } return 0; }
UVA - 10765 Doves and bombs (双联通分量)
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原文地址:http://blog.csdn.net/u013923947/article/details/45958205