first draft

Author: lrvideckis

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

@@ -20,6 +20,7 @@ template<class T, class F> struct tree {
   vector<T> s;
   tree(int n, T unit, F op):
     n(n), op(op), s(2 * n, unit) {}
+#include "seg_tree_uncommon/init.hpp"
   void update(int i, T val) {
     for (s[i += n] = val; i /= 2;)
       s[i] = op(s[2 * i], s[2 * i + 1]);

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

@@ -0,0 +1,7 @@
+#pragma once
+tree(const vector<T>& a, F op):
+  n(sz(a)), op(op), s(2 * n) {
+  rep(i, 0, n) s[i + n] = a[i];
+  for (int i = n - 1; i >= 1; i--)
+    s[i] = op(s[2 * i], s[2 * i + 1]);
+}