27 Remove Element – Easy

Problem:

Given an array and a value, remove all instances of that value in place and return the new length.

The order of elements can be changed. It doesn’t matter what you leave beyond the new length.

Thoughts:

This problem could be solved in O(n). But it’s always good to come up with a solution that is as good as possible, even inside of O(n) time. Solution below is following the principle that only do the swap that’s necessary.

Solutions:

public class Solution {
    public int removeElement(int[] nums, int val) {
        int start = 0, end = nums.length -1;
        while (start <= end) {
            if (nums[start] != val) {
                start ++;
                continue;
            }
            if (nums[end] == val) {
                end --;
                continue;
            }
            nums[start] = nums[end];
            start ++;
            end --;
        }
        return start;
    }
}