LeetCode 283. Move zero (simple, array) Day12

Title Description ： Given an array nums, Write a function that will 0 Move to end of array , While maintaining the relative order of non-zero elements .

Please note that , You must operate on the array in place without copying it .

Example 1:

 Input : nums = [0,1,0,3,12]
 Output : [1,3,12,0,0]

Example 2:

 Input : nums = [0]
 Output : [0]

title ：

Method 1 ： Double finger needling ( Think of your own way )

1、 Traversal array ;
2、 If num[i] != 0  Continue traversal , If num[i]==0 Do the following ;
3、 Set two pointers first ,left_pointer and left_move.left_pointer The element pointing to the current array is 0 The subscript of is i,left_move Subscript pointing to the next element ;
4、 From the current left_move Start to judge whether the current element is 0, If it's zero ,left_move Continue to move backward until you reach the first one that is not 0 The elements of ;
5、 In exchange for num[left_pointer ]  And  nums[left_move] Value  , Continue with the above , Until the end of the cycle 

Method 2 ： Double pointer method ( Refer to the online solution )

 We define two pointers ,i Pointers and k The pointer ,i The pointer is used to traverse the entire nums Array ,k The pointer is used to place nums Array elements . Then the non 0 The elements are placed in the original relative order nums Before the array ,
 The rest of the positions are set to 0. So we're done 0 The movement of elements , At the same time, non 0 The relative order of elements .

 The specific process is as follows ：
    1、 Define two pointers i and k, initialization i = 0,k = 0.
    2、i The pointer moves back , All over nums Array , If  nums[i] != 0, That is to say, we have encountered non 0 Elements , At this point we will nums[i] The element is placed in nums[k] Location , meanwhile k++ The latter .
    3、 The final will be k The elements after the position are assigned to 0.

 author ：lin-shen-shi-jian-lu-k
 link ：https://leetcode-cn.com/problems/move-zeroes/solution/283-yi-dong-ling-shuang-zhi-zhen-zuo-fa-6wmvs/

Code implementation ：

import java.util.Arrays;

public class MoveZeros {
    public static void main(String[] args) {
        int[] nums = {0, 1, 0,0, 3, 12, 15, 23, 0, 19, 0};
        moveZeroes1(nums);
        System.out.println(Arrays.toString(nums));
    }

    //  Method 1：  Double finger needling 1
    public static void moveZeroes1(int[] nums) {
        // 1.  If the array is empty or the length of the array is 1 The ending method 
        if (nums == null || nums.length == 1) {
            return;
        }

        // 2.  Traverse the array to find 
        for (int i = 0; i < nums.length; i++) {
            // 2.1  Find an array element with a value of 0 The elements of 
            if(nums[i] == 0){
                // 2.2  Declare two variables 
                int left_pointer = i, left_move = i + 1;
                while (left_move <  nums.length && nums[left_move] == 0){
                    left_move++;
                }

                if(left_move >= nums.length){  //  The following elements are 0 You can quit 
                    break;
                }else {  //  Exchange elements 
                    int temp = nums[left_move];
                    nums[left_move] = nums[left_pointer];
                    nums[left_pointer] = temp;
                }
            }
        }
    }

    //  Method 2：  Double finger needling 2
    public static void moveZeroes2(int[] nums){
        // 1.  If the array is empty or the length of the array is 1 The ending method 
        if (nums == null || nums.length == 1) {
            return;
        }

        // 2.  Set double pointer 
        int k = 0;  //  Non in record array 0 The number of 
        for(int i = 0; i < nums.length; i++){
            if(nums[i] != 0){
                nums[k++] = nums[i];
            }
        }

        int k_zero = nums.length -k;  //  In the record array 0 The number of 
        for(int i = nums.length-1; k_zero != 0; i--){
            nums[i] = 0;
            k_zero--;   //  Every time k You have to subtract one 
        }
    }
}

Link to the original text ：https://leetcode-cn.com/problems/move-zeroes/