adding first draft of KD tree

Author: lrvideckis

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

@@ -0,0 +1,40 @@
+#pragma once
+using T = int64_t;
+const T unit = 0;
+T op(T a, T b) { return a + b; }
+template<int K> struct KD_SEG {
+  int n;
+  vector<KD_SEG<K - 1>> s;
+  KD_SEG(int n, auto... a):
+    n(n), s(2 * n, KD_SEG<K - 1>(a...)) {}
+  void update(int p, auto... a) {
+    p += n;
+    s[p].update(a...);
+    for (p /= 2; p > 0; p /= 2)
+      s[p].pull(s[2 * p], s[2 * p + 1], a...);
+  }
+  T query(int l, int r, auto... a) {
+    T x = unit, y = unit;
+    for (l += n, r += n; l < r; l /= 2, r /= 2) {
+      if (l % 2) x = op(x, s[l++].query(a...));
+      if (r % 2) y = op(s[--r].query(a...), y);
+    }
+    return op(x, y);
+  }
+  void pull(const KD_SEG<K>& left, const KD_SEG<K>& right,
+    int p, auto... a) {
+    p += n;
+    s[p].pull(left.s[p], right.s[p], a...);
+    for (p /= 2; p > 0; p /= 2)
+      s[p].pull(s[2 * p], s[2 * p + 1], a...);
+  }
+};
+template<> struct KD_SEG<0> {
+  T val = unit;
+  void update(T v) { val = v; }
+  T query() { return val; }
+  void pull(const KD_SEG<0>& left, const KD_SEG<0>& right,
+    auto...) {
+    val = op(left.val, right.val);
+  }
+};

tests/library_checker_aizu_tests/data_structures/kd_bit.test.cpp

@@ -0,0 +1,39 @@
+#define PROBLEM \
+  "https://onlinejudge.u-aizu.ac.jp/problems/DPL_3_A"
+#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, m;
+  cin >> n >> m;
+  KD_BIT<2> bit(n, m);
+  //!   KD_BIT<2> bit(n, m);
+  //!   bit.update(i, j, 5);
+  //!   // 0 <= i < n
+  //!   // 0 <= j < m
+  //!   bit.query(i1, i2, j1, j2);
+  //!   // 0 <= i1 <= i2 <= n
+  //!   // 0 <= j1 <= j2 <= m
+  for (int i = 0; i < n; i++) {
+    for (int j = 0; j < m; j++) {
+      int c;
+      cin >> c;
+      if (c) bit.update(i, j, 1);
+    }
+  }
+  int res = 0;
+  for (int i = 0; i < n; i++) {
+    for (int j = 0; j < m; j++) {
+      int start = 0, end = min(n - i, m - j) + 1;
+      while (start + 1 < end) {
+        int mid = (start + end) / 2;
+        if (bit.query(i, i + mid, j, j + mid) == 0)
+          start = mid;
+        else end = mid;
+      }
+      res = max(res, start);
+    }
+  }
+  cout << res * res << '\n';
+  return 0;
+}