[LeetCode] 283. Move Zeroes 移動零

標籤：making   pytho   []   public   eating   obj   length   cpp   elements   

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.

Credits:
Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.

把一個數組裡所有的0都移到後面，不能改變非零數的相對位置關係，而且不能拷貝額外的數組。

要用替換法in-place，雙指標來做，前面的指標指向處理過的最後一個非零數字， 後面一個指標向後掃，遇到非零數字，和前面指標所指數字交換位置，前面指標後移1位。

或者不交換隻把非零的數字換到前面，最後子統一把後面的全部變成0。

Java: Time Complexity: O(n), Space Complixity: O(1)

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

Python:

class Solution(object):    def moveZeroes(self, nums):        """        :type nums: List[int]        :rtype: void Do not return anything, modify nums in-place instead.        """        pos = 0        for i in xrange(len(nums)):            if nums[i]:                nums[i], nums[pos] = nums[pos], nums[i]                pos += 1

C++:

class Solution {public:    void moveZeroes(vector<int>& nums) {        int pos = 0;        for (auto& num : nums) {            if (num) {                swap(nums[pos++], num);            }        }    }};

 

[LeetCode] 283. Move Zeroes 移動零