leetcode 27:Remove Element

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 in place with constant memory.

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

Example:
Given input array nums = [3,2,2,3], val = 3

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

解題思路

利用兩個指針 i,j: i向後掃描，只要i指向的當前元素不等於指定元素，則交換i,j指向的元素，j++.最後 ,所有指定的元素都被移動到數組後排，j指向指定元素的首位。

代碼實現

public class Solution {
    public int removeElement(int[] nums, int val) {
        int j=0;
        int length = nums.length;
        for(int i = 0 ; i < length ; i++){
            if(nums[i] != val){
                nums[j++] = nums[i];
            }
        }
        return j;
    }
}