From abf464e844eccf360333c75fd126d726bfab3175 Mon Sep 17 00:00:00 2001
From: indy256 <indy256@gmail.com>
Date: Sun, 8 Oct 2023 14:45:02 -0400
Subject: [PATCH] Improve segment_tree

---
 cpp/structures/segment_tree.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/cpp/structures/segment_tree.h b/cpp/structures/segment_tree.h
index 618d2b5a..6e93d57e 100644
--- a/cpp/structures/segment_tree.h
+++ b/cpp/structures/segment_tree.h
@@ -9,6 +9,12 @@ struct segtree {
         long long sum = 0;
         long long add = 0;
 
+        // set initial value for a leave
+        void initialize(long long v) {
+            mx = v;
+        }
+
+        // apply aggregate operation to the node
         void apply(int l, int r, long long v) {
             mx += v;
             sum += (r - l + 1) * v;
@@ -16,6 +22,7 @@ struct segtree {
         }
     };
 
+    // construct a node from its children
     static node unite(const node &a, const node &b) {
         node res;
         res.mx = max(a.mx, b.mx);
@@ -52,7 +59,7 @@ struct segtree {
     template <class T>
     void build(int x, int l, int r, const vector<T> &v) {
         if (l == r) {
-            tree[x].apply(l, r, v[l]);
+            tree[x].initialize([l]);
             return;
         }
         int m = (l + r) >> 1;