Trapping Rain Water II In 2D Elevation Maps With PHP
Trapping Rain Water II: Compute volume of water trapped after raining on 2D elevation map using BFS and priority queue.
Neighboring Bitwise XOR: Valid Binary Array Existence
The XOR of all elements in derived must equal 0 for a valid original array to exist. If the result is 0, return true; otherwise, return false.
Can A Parentheses String Be Valid With Locked Indices?
A string is valid if it's empty or can be written as AB where A and B are valid strings, or (A) where A is a valid string. Given a string s and locked string, return true if s can be made valid.
Minimum Remove To Make Valid Parentheses
Remove min parentheses to make valid string: remove unnecessary ( and ) while keeping valid chars. Two-pass approach: first pass removes invalid closing ), second pass removes invalid opening (.
Counting Nice Subarrays With Sliding Window And Prefix Sums
The problem requires finding the number of subarrays in an integer array that contain exactly k odd numbers. A sliding window approach with prefix sums efficiently counts these "nice" subarrays.
Can Construct K Palindrome Strings From Given String
Construct K Palindrome Strings: Use hash table to count char frequencies & odd counts. If k > len(s) or odd counts > k, return false. Otherwise, true.
Counting Words With A Given Prefix In PHP: 2
Iterate through array, check if prefix is part of each word using substr function. Time complexity: O(n * m).