From ef8275fc7ae6952af59ab932f8e59371deab4726 Mon Sep 17 00:00:00 2001
From: Baoshuo <i@baoshuo.ren>
Date: Sun, 20 Nov 2022 09:14:14 +0800
Subject: [PATCH] =?UTF-8?q?P3379=20=E3=80=90=E6=A8=A1=E6=9D=BF=E3=80=91?=
 =?UTF-8?q?=E6=9C=80=E8=BF=91=E5=85=AC=E5=85=B1=E7=A5=96=E5=85=88=EF=BC=88?=
 =?UTF-8?q?LCA=EF=BC=89?=
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https://www.luogu.com.cn/record/94730020
---
 Luogu/P3379/P3379.cpp | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/Luogu/P3379/P3379.cpp b/Luogu/P3379/P3379.cpp
index 6ea26669..8f45d9b7 100644
--- a/Luogu/P3379/P3379.cpp
+++ b/Luogu/P3379/P3379.cpp
@@ -10,13 +10,14 @@ const char endl = '\n';
 const int N = 5e5 + 5;
 const int INF = 0x3f3f3f3f;
 
-int n, m, s, dep[N], fa[N][25];
+int n, m, s, dep[N], fa[N][std::__lg(N) + 1];
 std::vector<int> g[N];
 
 void bfs(int s) {
     std::fill_n(dep, N, INF);
 
     std::queue<int> q;
+
     q.emplace(s);
     dep[0] = 0;
     dep[s] = 1;
@@ -31,7 +32,7 @@ void bfs(int s) {
                 q.emplace(v);
                 fa[v][0] = u;
 
-                for (int k = 1; k <= 19; k++) {
+                for (int k = 1; k <= std::__lg(n); k++) {
                     fa[v][k] = fa[fa[v][k - 1]][k - 1];
                 }
             }
@@ -42,7 +43,7 @@ void bfs(int s) {
 int lca(int x, int y) {
     if (dep[x] < dep[y]) std::swap(x, y);
 
-    for (int k = 19; k >= 0; k--) {
+    for (int k = std::__lg(n); k >= 0; k--) {
         if (dep[fa[x][k]] >= dep[y]) {
             x = fa[x][k];
         }
@@ -50,7 +51,7 @@ int lca(int x, int y) {
 
     if (x == y) return x;
 
-    for (int k = 19; k >= 0; k--) {
+    for (int k = std::__lg(n); k >= 0; k--) {
         if (fa[x][k] != fa[y][k]) {
             x = fa[x][k];
             y = fa[y][k];