#dsa/recursion

344 Reverse String

Problem Statement

Write a function that reverses a string. The input string is given as an array of characters s. You must do this by modifying the input array in-place with O(1) extra memory.
Input: s = ["h","e","l","l","o"]
Output: ["o","l","l","e","h"]

Approach

The BF approach would be to use a Left and Right Pointer to loop through the array while L < R. At each iteration we would swap the chars and increase/decrease the pointers.
The solution we are interested in is of recursive nature though:

We create a helper function, that takes in the left and right pointer, checks the base case of if (l < r) and then does the swap and calls itself with the updated pointers.

Solution

var reverseString = function(s) {
	function recursiveSwap(l,r){
		if (l < r) {
			[s[l], s[r]] = [s[r], s[l]]
			recursiveSwap(l + 1, r - 1)
			}
	}
	recursiveSwap(0, s.length - 1)
};

Questions

References

Recursion