first draft

Author: lrvideckis

library/data_structures_[l,r)/bit_uncommon/kd_bit.hpp

@@ -0,0 +1,20 @@
+template<int K> struct KD_BIT;
+template<> struct KD_BIT<0> {
+  ll s = 0;
+  void update(ll v) { s += v; }
+  ll query() { return s; }
+};
+template<int K> struct KD_BIT {
+  vector<KD_BIT<K - 1>> s;
+  template<class... A>
+  KD_BIT(int n, A... a): s(n, KD_BIT<K - 1>(a...)) {}
+  template<class... A> void update(int i, A... a) {
+    for (; i < sz(s); i |= i + 1) s[i].update(a...);
+  }
+  template<class... A> ll query(int l, int r, A... a) {
+    ll ans = 0;
+    for (; l < r; r &= r - 1) ans += s[r - 1].query(a...);
+    for (; r < l; l &= l - 1) ans -= s[l - 1].query(a...);
+    return ans;
+  }
+};

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

@@ -1,7 +1,10 @@
 int walk(int l, int r, const auto& f) {
+  bool initialized = 0;
+  T x;
   while (l <= r) {
     int u = l + n, v = __lg(min(u & -u, r - l + 1));
-    if (f(s[u >> v])) l += 1 << v;
+    T y = initialized ? op(x, f(s[u >> v])) : s[u >> v];
+    if (f(y)) l += 1 << v, x = y, initialized = 1;
     else r = l + (1 << v) - 2;
   }
   return l;

tests/library_checker_aizu_tests/data_structures/kd_bit_1d.test.cpp

@@ -0,0 +1,34 @@
+#define PROBLEM \
+  "https://judge.yosupo.jp/problem/point_add_range_sum"
+#include "../template.hpp"
+#include "../../../library/data_structures_[l,r)/bit_uncommon/kd_bit.hpp"
+int main() {
+  cin.tie(0)->sync_with_stdio(0);
+  int n, q;
+  cin >> n >> q;
+  KD_BIT<1> bit1(n);
+  KD_BIT<2> bit2(1, n);
+  for (int i = 0; i < n; i++) {
+    int val;
+    cin >> val;
+    bit1.update(i, val);
+    bit2.update(0, i, val);
+  }
+  while (q--) {
+    int type;
+    cin >> type;
+    if (type == 0) {
+      int p, x;
+      cin >> p >> x;
+      bit1.update(p, x);
+      bit2.update(0, p, x);
+    } else {
+      int l, r;
+      cin >> l >> r;
+      ll res = bit1.query(l, r);
+      assert(res == bit2.query(0, 1, l, r));
+      cout << res << '\n';
+    }
+  }
+  return 0;
+}

tests/library_checker_aizu_tests/data_structures/simple_tree_inc_walk.test.cpp

@@ -32,13 +32,8 @@ int main() {
       if (total == 0) {
         cout << -1 << '\n';
       } else {
-        int pref_sum = 0;
         cout << st.walk(0, k, [&](int sum) {
-          if (pref_sum + sum < total) {
-            pref_sum += sum;
-            return 1;
-          }
-          return 0;
+          return sum < total;
         }) << '\n';
       }
     }