Seg tree nit (#173)

* Update seg_tree.hpp

* [auto-verifier] verify commit 1296461

* Format constructor for better readability

* [auto-verifier] verify commit 78ccda0

* update docs

Updated segment tree example code in comments.

* [auto-verifier] verify commit 611f33d

---------

Co-authored-by: GitHub <noreply@github.com>

Author: lrvideckis

.verify-helper/timestamps.remote.json

@@ -44,8 +44,8 @@
 "tests/library_checker_aizu_tests/data_structures/rmq_sparse_table.test.cpp": "2026-01-18 11:15:41 +0000",
 "tests/library_checker_aizu_tests/data_structures/rmq_sparse_table_inc.test.cpp": "2026-01-18 11:15:41 +0000",
 "tests/library_checker_aizu_tests/data_structures/simple_tree.test.cpp": "2026-01-18 11:15:41 +0000",
-"tests/library_checker_aizu_tests/data_structures/simple_tree_inc.test.cpp": "2026-01-18 11:15:41 +0000",
-"tests/library_checker_aizu_tests/data_structures/simple_tree_inc_line.test.cpp": "2026-01-18 11:15:41 +0000",
+"tests/library_checker_aizu_tests/data_structures/simple_tree_inc.test.cpp": "2026-01-21 23:24:08 -0700",
+"tests/library_checker_aizu_tests/data_structures/simple_tree_inc_line.test.cpp": "2026-01-21 23:24:08 -0700",
 "tests/library_checker_aizu_tests/data_structures/simple_tree_line.test.cpp": "2026-01-18 11:15:41 +0000",
 "tests/library_checker_aizu_tests/flow/dinic_aizu.test.cpp": "2024-11-17 14:04:03 -0600",
 "tests/library_checker_aizu_tests/flow/hungarian.test.cpp": "2024-11-17 14:04:03 -0600",

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

@@ -2,12 +2,11 @@
 //! https://codeforces.com/blog/entry/118682
 //! @code
 //!   {
-//!     tree st(n, pii{}, [&](pii& l, pii& r) {
-//!       return min(l, r);
+//!     tree st(n, 0LL, [&](ll l, ll r) {
+//!       return l + r;
 //!     });
 //!   }
-//!   tree st(n, int{}, ranges::min);
-//!   rep(i, 0, n) st.update(i, a[i]);
+//!   tree st(n, INT_MAX, ranges::min);
 //! @endcode
 //! @time O(n + q log n)
 //! @space O(n)
@@ -19,7 +18,8 @@ template<class T, class F> struct tree {
   int n;
   F op;
   vector<T> s;
-  tree(int n, T, F op): n(n), op(op), s(2 * n) {}
+  tree(int n, T unit, F op):
+    n(n), op(op), s(2 * n, unit) {}
   void update(int i, T val) {
     for (s[i += n] = val; i /= 2;)
       s[i] = op(s[2 * i], s[2 * i + 1]);