27 Remove Element

27. Remove Element

1. Question

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

Do not allocate extra space for another array, you must do this by modifying the input array in-placewith O(1) extra memory.

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

Example:

Given nums = [3,2,2,3], val = 3,

Your function should return length = 2, with the first two elements of nums being 2.

2. Implementation

public class Solution {
    public int removeElement(int[] nums, int val) {
        if (nums == null || nums.length == 0) {
            return 0;
        }

        int index = 0;
        for (int num : nums) {
            if (num != val) {
                nums[index++] = num;
            }
        }
        return index;
    }
}

3. Time & Space Complexity

时间复杂度O(n), 空间复杂度O(1)