add walk for [l,r] now

Author: lrvideckis

library/data_structures_[l,r]/bit.hpp

@@ -17,5 +17,6 @@ struct BIT {
   ll query(int l, int r) {
     return query(r) - query(l - 1);
   }
+#include "bit_uncommon/walk_lambda.hpp"
 #include "../data_structures_[l,r)/bit_uncommon/walk.hpp"
 };

library/data_structures_[l,r]/bit_uncommon/walk_lambda.hpp

@@ -0,0 +1,6 @@
+void walk(const auto& f) {
+  ll sum = 0;
+  for (int i = bit_floor(size(s)), r = 0; i; i /= 2)
+    if (r + i <= sz(s) && f(r + i - 1, sum + s[r + i - 1]))
+      sum += s[(r += i) - 1];
+}

tests/library_checker_aizu_tests/data_structures/bit_inc_walk.test.cpp

@@ -0,0 +1,51 @@
+#define PROBLEM \
+  "https://judge.yosupo.jp/problem/predecessor_problem"
+#include "../template.hpp"
+#include "../../../library/data_structures_[l,r]/bit.hpp"
+int main() {
+  cin.tie(0)->sync_with_stdio(0);
+  int n, q;
+  string s;
+  cin >> n >> q >> s;
+  vector<ll> init(n);
+  for (int i = 0; i < n; i++) init[i] = s[i] - '0';
+  BIT bit(init);
+  while (q--) {
+    int type, k;
+    cin >> type >> k;
+    if (type == 0) {
+      if (bit.query(k, k) == 0) bit.update(k, 1);
+    } else if (type == 1) {
+      if (bit.query(k, k) == 1) bit.update(k, -1);
+    } else if (type == 2) {
+      cout << bit.query(k, k) << '\n';
+    } else if (type == 3) {
+      if (bit.query(k, n - 1) == 0) cout << -1 << '\n';
+      else {
+        ll order = bit.query(k - 1);
+        int res = -1;
+        bit.walk([&](int r, ll sum) {
+          if (sum <= order) return 1;
+          res = r;
+          return 0;
+        });
+        cout << res << '\n';
+      }
+    } else {
+      if (bit.query(k) == 0) cout << -1 << '\n';
+      else {
+        ll order = bit.query(k);
+        int res = -1;
+        bit.walk([&](int r, ll sum) {
+          if (sum >= order) {
+            res = r;
+            return 0;
+          }
+          return 1;
+        });
+        cout << res << '\n';
+      }
+    }
+  }
+  return 0;
+}