nit

Author: lrvideckis

library/data_structures_[l,r)/seg_tree_uncommon/walk.hpp

@@ -1,8 +1,9 @@
 int walk(int l, int r, const auto& f) {
+  T x = unit;
   while (l < r) {
-    int u = l + n, x = __lg(min(u & -u, r - l));
-    if (f(s[u >> x])) l += 1 << x;
-    else r = l + (1 << x) - 1;
+    int u = l + n, v = __lg(min(u & -u, r - l));
+    if (T y = op(x, s[u >> v]); f(y)) x = y, l += 1 << v;
+    else r = l + (1 << v) - 1;
   }
   return l;
 }

library/data_structures_[l,r]/seg_tree_uncommon/walk.hpp

@@ -1,8 +1,8 @@
 int walk(int l, int r, const auto& f) {
   while (l <= r) {
-    int u = l + n, x = __lg(min(u & -u, r - l + 1));
-    if (f(s[u >> x])) l += 1 << x;
-    else r = l + (1 << x) - 2;
+    int u = l + n, v = __lg(min(u & -u, r - l + 1));
+    if (f(s[u >> v])) l += 1 << v;
+    else r = l + (1 << v) - 2;
   }
   return l;
 }

tests/library_checker_aizu_tests/data_structures/simple_tree_walk.test.cpp

@@ -31,11 +31,8 @@ int main() {
       if (total == 0) {
         cout << -1 << '\n';
       } else {
-        int pref_sum = 0;
         cout << st.walk(0, k + 1, [&](int sum) {
-          if (pref_sum + sum < total)
-            return pref_sum += sum, 1;
-          return 0;
+          return sum < total;
         }) << '\n';
       }
     }