Given a string s representing movements on an infinite grid with 'N', 'S', 'E', and 'W' characters, find the maximum Manhattan distance from the origin that can be achieved by changing at most k characters.
Approach involves iterating through the string, updating position based on directions, calculating Manhattan distance at each step, accounting for changes allowed, and updating the maximum distance accordingly.
The solution efficiently determines the maximum Manhattan distance with the constraint of at most k changes to the movement directions in the string.
The algorithm runs in linear time, making it suitable for large inputs.
Example scenarios such as changing 'S' to 'N' in 'NWSE' to get a distance of 3 and changing 'NSWWEW' result in an output of 6 are provided.
Constraints include 1 <= s.length <= 105 and 0 <= k <= s.length, with hints suggesting brute forcing directions and maximizing distance changes.
The algorithm involves optimizing movements by potentially changing directions to increase the Manhattan distance from the origin.
Code example in PHP showcases the implementation and testing with test cases to demonstrate the solution.
The approach efficiently balances distance optimization with the constraints of allowed changes and total movements in the string.
The solution offers a systematic way to determine the maximum Manhattan distance achievable with limited direction changes.