【BZOJ2772】policija【BCC】【割顶】【离线】【分治】【并查集】

来源：互联网发布：win10网卡mac地址编辑：程序博客网时间：2024/05/22 16:07

【题目链接】

先跑出dfs树。

对于两个操作，先把不连通的情况用并查集搞掉。

另外对于操作1，如果G1-G2是非树边，那么形成了环，这种情况肯定是yes。

然后跑Tarjan，对每个操作形成的子树讨论一下就完了。

#include <cstdio>/* Pigonometry */#include <cstring>#include <algorithm>#include <vector>using namespace std;const int maxn = 100005, maxm = 500005, maxc = 300005, maxs = 300000;int n, m, head[maxm], cnt, pre[maxn], fa[maxn];int ans[maxc], A[maxc], B[maxc];int dfn[maxn], low[maxn], clo, sta[maxs], top;bool cut[maxn], ins[maxn];struct _edge {int v, next;} g[maxm << 1];vector<int> c1[maxn], c2[maxn];inline int iread() {int f = 1, x = 0; char ch = getchar();for(; ch < '0' || ch > '9'; ch = getchar()) f = ch == '-' ? -1 : 1;for(; ch >= '0' && ch <= '9'; ch = getchar()) x = x * 10 + ch - '0';return f * x;}inline void add(int u, int v) {g[cnt] = (_edge){v, head[u]};head[u] = cnt++;}inline int find(int x) {return fa[x] == x ? x : fa[x] = find(fa[x]);}inline void dfs(int x) {for(int i = head[x]; ~i; i = g[i].next) if(!pre[g[i].v]) {pre[g[i].v] = x;dfs(g[i].v);}}inline bool check(int x, int u, int v) {if(find(u) == find(v)) return 1;if((!dfn[u] || dfn[u] < dfn[x]) && (!dfn[v] || dfn[v] < dfn[x])) return 1;return 0;}inline void tarjan(int x) {dfn[x] = low[x] = ++clo;ins[sta[++top] = x] = 1;for(int i = head[x]; ~i; i = g[i].next) if(g[i].v ^ pre[x]) {int v = g[i].v;if(!dfn[v]) {tarjan(v);low[x] = min(low[x], low[v]);if(low[v] >= dfn[x]) cut[v] = 1;}else if(ins[v]) low[x] = min(low[x], dfn[v]);}for(int i = 0; i < c2[x].size(); i++) {int u = A[c2[x][i]], v = B[c2[x][i]];if(check(x, u, v) && u != x && v != x) continue;if(u == x || v == x) ans[c2[x][i]] = 0;if(dfn[u] > dfn[x] && cut[find(u)]) ans[c2[x][i]] = 0;if(dfn[v] > dfn[x] && cut[find(v)]) ans[c2[x][i]] = 0;}for(int i = head[x]; ~i; i = g[i].next) if(dfn[g[i].v] > dfn[x])fa[find(g[i].v)] = find(x);if(dfn[x] == low[x]) {for(int i = 0; i < c1[x].size(); i++) {int u = A[c1[x][i]], v = B[c1[x][i]];if(check(x, u, v)) continue;ans[c1[x][i]] = 0;}while(1) {int u = sta[top--];ins[u] = 0;if(u == x) break;}}}int main() {freopen("2.in", "r", stdin);freopen("2.out", "w", stdout);n = iread(); m = iread();for(int i = 1; i <= n; i++) head[i] = -1, fa[i] = i; cnt = top = 0;for(int i = 1; i <= m; i++) {int u = iread(), v = iread();add(u, v); add(v, u);fa[find(u)] = find(v);}for(int i = 1; i <= n; i++) if(!pre[i]) pre[i] = -1, dfs(i);int T = iread();for(int i = 1; i <= T; i++) {int opt = iread(); A[i] = iread(); B[i] = iread();ans[i] = 1;if(opt == 1) {int u = iread(), v = iread();if(find(A[i]) != find(B[i])) {ans[i] = 0;continue;}if(pre[v] != u) swap(v, u);if(pre[v] != u) continue;c1[v].push_back(i);} else {int u = iread();if(find(A[i]) != find(B[i])) {ans[i] = 0;continue;}c2[u].push_back(i);}}for(int i = 1; i <= n; i++) fa[i] = i;for(int i = 1; i <= n; i++) if(!~pre[i]) tarjan(i);for(int i = 1; i <= T; i++) printf(ans[i] ? "yes\n" : "no\n");return 0;}

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