more golf!

Author: lrvideckis

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

@@ -1,24 +1,8 @@
-int go(int l, int r) {
-//return __lg(min(l & -l, r - l + 1));
-//return __lg(min((l + n) & -(l + n), r - l + 1));
-  return min(__builtin_ctz(l + n), __lg(r - l + 1));
-}
 int walk(int l, int r, const auto& f) {
-  /*
-  for (l += n, r += n; l <= r;)
-    if (int u = nxt(l, r); f(s[u])) {
-      while (u < n)
-        if (f(s[2 * u])) u *= 2;
-        else (u *= 2)++;
-      return u - n;
-    }
-  */
-  int good=0;
-  while (l <= r-good) {
-    int u = l + n, x = __lg(min(u & -u, r - l +1-good));
-    if (f(s[u >> x])) good=1,r = l + (1 << x) - 1;
+  while (l <= r) {
+    int u = l + n, x = __lg(min(u & -u, r - l + 1));
+    if (f(s[u >> x])) r = l + (1 << x) - 2;
     else l += 1 << x;
   }
-  return good ? l : -1;
- // return l;
+  return l;
 }

tests/library_checker_aizu_tests/data_structures/simple_tree_inc_walk.test.cpp

@@ -22,9 +22,11 @@ int main() {
       cout << st.query(k, k) << '\n';
     } else if (type == 3) {
       // returns first element in [k,n-1] such that sum > 0
-      cout << st.walk(k, n - 1, [&](int sum) {
+      int idx = st.walk(k, n - 1, [&](int sum) {
         return sum > 0;
-      }) << '\n';
+      });
+      if(idx == n) idx = -1;
+      cout<<idx<<'\n';
     } else {
       assert(type == 4);
       int total = st.query(0, k);