Leetcode Move Zeroes

Given an array nums, write a function to move all 0's to the end of it while maintaining the relative order of the non-zero elements.

For example, given nums = [0, 1, 0, 3, 12], after calling your function, nums should be [1, 3, 12, 0, 0].

Note:

You must do this in-place without making a copy of the array.
Minimize the total number of operations.

解题思路：

题目可以在O(n)时间复杂度内求解

算法步骤：x = i y = j

使用两个"指针"x和y，初始令y = 0

利用x遍历数组nums：

若nums[x]非0，则交换nums[x]与nums[y]，并令y+1

算法简析：

y指针指向首个0元素可能存在的位置

遍历过程中，算法确保[y, x)范围内的元素均为0

Java code

public void moveZeroes(int[] nums) {
        int i = 0, j = 0;
        for(i = 0; i< nums.length; i++){
            if(nums[i] != 0){
                if(j != i){
                    nums[j] = nums[i];
                    nums[i] = 0;
                }
                j++;
            }
        }
    }

Reference:

1. http://bookshadow.com/weblog/2015/09/19/leetcode-move-zeroes/

2. https://leetcode.com/discuss/59543/move-zeros-solution-in-java