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https://git.sb/baoshuo/OI-codes.git
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parent
338a79dac9
commit
66a10cd04d
@ -1,56 +1,62 @@
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#pragma GCC optimize("Ofast")
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#include <bits/stdc++.h>
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using namespace std;
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int n, m, s, x, y;
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int n, m, s, root, a, b, dep[500005], fa[500005][20];
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vector<int> tr[500005];
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struct node {
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int depth, father;
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vector<int> next;
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} tree[500005];
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bool vis[500005];
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void dfs(int depth, int root, int father) {
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tree[root].father = father;
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for (int i = 0; i < tree[root].next.size(); i++) {
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if (tree[root].next[i] != father) {
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tree[tree[root].next[i]].depth = depth + 1;
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tree[tree[root].next[i]].father = root;
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dfs(depth + 1, tree[root].next[i], root);
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void bfs(int root) {
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memset(dep, 0x3f, sizeof(dep));
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dep[0] = 0;
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dep[root] = 1;
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queue<int> q;
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q.push(root);
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while (!q.empty()) {
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int t = q.front();
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q.pop();
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for (int i : tr[t]) {
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if (dep[i] > dep[t] + 1) {
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dep[i] = dep[t] + 1;
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q.push(i);
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fa[i][0] = t;
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for (int k = 1; k <= 19; k++) {
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fa[i][k] = fa[fa[i][k - 1]][k - 1];
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}
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}
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}
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}
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return;
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}
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void dfs2(int now) {
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vis[now] = true;
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if(now == s) return;
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else dfs2(tree[now].father);
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}
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int dfs3(int now) {
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if(vis[now]) return now;
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else return dfs3(tree[now].father);
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int lca(int a, int b) {
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if (dep[a] < dep[b]) swap(a, b);
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for (int k = 19; k >= 0; k--) {
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if (dep[fa[a][k]] >= dep[b]) {
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a = fa[a][k];
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}
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}
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if (a == b) return a;
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for (int k = 19; k >= 0; k--) {
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if (fa[a][k] != fa[b][k]) {
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a = fa[a][k];
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b = fa[b][k];
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}
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}
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return fa[a][0];
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}
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int main() {
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scanf("%d%d%d", &n, &m, &s);
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scanf("%d%d%d", &n, &m, &root);
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for (int i = 1; i < n; i++) {
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scanf("%d%d", &x, &y);
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tree[x].next.push_back(y);
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tree[y].next.push_back(x);
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scanf("%d%d", &a, &b);
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tr[a].push_back(b);
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tr[b].push_back(a);
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}
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dfs(1, s, s);
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for(int i = 0 ; i < m ; i++) {
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scanf("%d%d", &x, &y);
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memset(vis, 0x00, sizeof(vis));
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if(tree[x].depth > tree[y].depth) {
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dfs2(x);
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printf("%d\n", dfs3(y));
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} else {
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dfs2(y);
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printf("%d\n", dfs3(x));
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}
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bfs(root);
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for (int i = 0; i < m; i++) {
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scanf("%d%d", &a, &b);
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printf("%d\n", lca(a, b));
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}
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return 0;
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}
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