fix doc nits

Author: Cameron Custer

library/contest/README.md

@@ -9,7 +9,7 @@ freopen("output.txt", "w", stdout);
 If you changed something for debugging, add a `cout << "don't submit" << endl;`
 or `assert(0);` at the end of the code
 
-for policy base DS:
+for policy-based DS:
 ```
 #include <bits/extc++.h>
 ```
@@ -25,7 +25,7 @@ don't use cin for doubles/floats, it's slow, read into string, then convert to d
 cin.exceptions(cin.failbit);
 ```
 
-- use pramgas for C++ speed boost
+- use pragmas for C++ speed boost
 ```
 #pragma GCC optimize("O3,unroll-loops")
 #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")

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

@@ -7,6 +7,7 @@
 //!   int r = bit.walk2(sum);
 //!   // Returns min r s.t. sum of [0,r] >= sum
 //!   // Returns n if sum of [0,n-1] < sum
+//!   // Returns -1 if sum <= 0
 //! @endcode
 //! @time O(n + q log n)
 //! @space O(n)

library/data_structures_[l,r)/uncommon/priority_queue_of_updates.hpp

@@ -1,13 +1,12 @@
 #pragma once
 //! https://codeforces.com/blog/entry/111117
 //! @code
-//!     dsu_restorable dsu_r(n);
-//!     pq_updates<dsu_restorable, int, int> pq(dsu_r);
-//!     rep (i, 0, n) pq.ds.add(i, initial_nums[i]);
-//!     //or
-//!     pq.ds.subtree = initial_nums;
-//!     pq.push_update(u, v, curr_pri);
-//!     cout << pq.ds.sum(v) << '\n';
+//!   // DS = any struct with member functions join, undo
+//!   DS ds;
+//!   // int = argument type of DS::join
+//!   pq_updates<DS, int> pq(ds);
+//!   pq.push_update(val, priority);
+//!   pq.pop_update();
 //! @endcode
 //! @time n interweaved calls to pop_update, push_update
 //! take O(T(n)*nlogn) where O(T(n)) = time complexity of

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

@@ -7,6 +7,7 @@
 //!   int r = bit.walk2(sum);
 //!   // Returns min r s.t. sum of [0,r] >= sum
 //!   // Returns n if sum of [0,n-1] < sum
+//!   // Returns -1 if sum <= 0
 //! @endcode
 //! @time O(n + q log n)
 //! @space O(n)

library/graphs/uncommon/block_vertex_tree.hpp

@@ -15,7 +15,7 @@
 //! [0, n) are original nodes
 //! [n, n + num_bccs) are BCC nodes
 //! @time O(n + m)
-//! @time O(n)
+//! @space O(n)
 auto block_vertex_tree(const auto& g, int num_bccs,
   const vi& bcc_id) {
   int n = sz(g);

library/math/tetration_mod.hpp

@@ -7,7 +7,7 @@
 //!
 //! returns b ^ (b ^ (... ^ b))) % mod, where
 //!   the height of the tower is e.
-//
+//!
 //! @time O(sqrt(mod) * log(mod))
 //! @space O(log(mod))
 ll bin_exp(ll b, ll e, int mod) {