Fix bug in segment tree walk function

lrvideckis · web-flow · commit 267032c5a5b9 · 2026-02-07T02:48:32.000-07:00
diff --git a/library/data_structures_[l,r]/seg_tree_uncommon/walk.hpp b/library/data_structures_[l,r]/seg_tree_uncommon/walk.hpp
@@ -14,7 +14,7 @@ int walk(int l, int r, const auto& f) {
     }
   */
   while (l <= r) {
-    int u = l + n, x = __lg(min(u & -u, int(bit_ceil(r - l + 1u)-1));
+    int u = l + n, x = __lg(min(u & -u, r - l));
     if (f(s[u >> x])) r = l + (1 << x) - 1;
     else l += 1 << x;
   }

Original file line number	Diff line number	Diff line change
`@@ -14,7 +14,7 @@ int walk(int l, int r, const auto& f) {`
`14`	`14`	`}`
`15`	`15`	`*/`
`16`	`16`	`while (l <= r) {`
`17`		`- int u = l + n, x = __lg(min(u & -u, int(bit_ceil(r - l + 1u)-1));`
	`17`	`+ int u = l + n, x = __lg(min(u & -u, r - l));`
`18`	`18`	`if (f(s[u >> x])) r = l + (1 << x) - 1;`
`19`	`19`	`else l += 1 << x;`
`20`	`20`	`}`