目录调整

00lanqiao chap/test99-5-3.cpp

@@ -0,0 +1,58 @@
+// lanqiao4385 最近公共祖先LCA查询
+#include<bits/stdc++.h>
+using namespace std;
+const int N = 1e5 + 9;
+int dep[N], fa[N][24];
+vector<int> g[N];
+
+void dfs(int x, int p){
+    dep[x] = dep[p] + 1;
+    fa[x][0] = p;
+    for(int i = 1; i <= 20; i++) fa[x][i] = fa[fa[x][i-1]][i-1];
+    for(const auto&y:g[x]){
+        if(y == p) continue;
+        dfs(y, x);
+    } 
+}
+
+int lca(int x, int y){
+    if(dep[x] < dep[y]) swap(x, y);
+    for(int i = 20; i >= 0; i--){
+        if(dep[fa[x][i]] >= dep[y]){
+            x = fa[x][i];
+        }
+    } 
+    if(x == y) return x;
+    for(int i = 20; i >= 0; i--){
+        if(fa[x][i] != fa[y][i]){
+            x = fa[x][i], y = fa[y][i];
+        }
+    }
+    return fa[x][0];
+}
+
+int main(){ 
+    int n; cin >> n;
+    for(int i = 1; i < n; i++){
+        int u, v; cin >> u >> v;
+        g[u].push_back(v); g[v].push_back(u);
+    }
+    dfs(1, 0);
+    int m; cin >> m;
+    while(m--){
+        int x, y; cin >> x >> y;
+        cout << lca(x, y) << '\n';
+    }
+    return 0;
+}
+/* test samples ->  2 1 1
+5
+1 2
+1 3
+2 4
+2 5
+3
+4 5
+3 4
+3 5
+*/