UVA10765 Doves and bombs

题目链接

给定一个连通图，求删除每一个点所能得到的连通块的个数

如果那个点是割点，那么就求一下与它直接相连的点分布于多少个连通分量内，如果不是割点，那结果就是1

#include <cstdio>#include <cstring>#include <algorithm>#include <vector>#include <stack>#include <set>using namespace std;const int maxn = 111111;int pre[maxn], bccno[maxn], bcc_cnt, iscut[maxn], dfs_clock;vector<int> G[maxn], bcc[maxn];struct edge{int u, v;edge(int u, int v) : u(u), v(v){}};stack<edge> S;int n, m;struct node{int pos, val;bool operator < (const node &a)const{if (val == a.val)return pos < a.pos;return val > a.val;}}T[maxn];int dfs(int u, int fa){int lowu = pre[u] = ++dfs_clock;int chd = 0;for (int i = 0; i < G[u].size(); i++){int v = G[u][i];edge e = edge(u, v);if (!pre[v]){S.push(e);chd += 1;int lowv = dfs(v, u);lowu = min(lowu, lowv);if (lowv >= pre[u]){iscut[u] = 1;bcc_cnt += 1; bcc[bcc_cnt].clear();for(;;){edge x = S.top(); S.pop();if (bccno[x.u] != bcc_cnt){bcc[bcc_cnt].push_back(x.u); bccno[x.u] = bcc_cnt;}if (bccno[x.v] != bcc_cnt){bcc[bcc_cnt].push_back(x.v); bccno[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 && chd == 1) iscut[u] = 0;return lowu;}set<int> ss;void find_bcc(int n){memset(pre, 0, sizeof(pre));memset(iscut, 0, sizeof(iscut));memset(bccno, 0, sizeof(bccno));dfs_clock = bcc_cnt = 0;ss.clear();for (int i = 0; i < n; i++)if (!pre[i]) dfs(2, -1);for (int i = 0; i < n; i++){if (iscut[i]){for (int j = 0; j < G[i].size(); j++){int v = G[i][j];ss.insert(bccno[v]);}T[i].pos = i; T[i].val = ss.size();ss.clear();}else{T[i].pos = i;T[i].val = 1;}}sort(T, T + n);for (int i = 0; i < m; i++)printf("%d %d\n", T[i].pos, T[i].val);printf("\n");}int main(){while (~scanf("%d%d", &n, &m)){if (!n && !m) break; int x, y;for (int i = 0; i <= n; i++)G[i].clear();while(~scanf("%d%d", &x, &y)){if (x == -1 && y == -1) break;G[x].push_back(y);G[y].push_back(x);}find_bcc(n);}return 0;}