LeetCode 27. Remove Element

Posted 2022-12-13 月牙儿June

分类： Array ; Two Points

问题描述：

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.

Hint:

1. Try two pointers.
2. Did you use the property of "the order of elements can be changed"?
3. What happens when the elements to remove are rare?

方法思路：

Java代码示例：

public class Solution 
    /*这种方法最后返回的数组会有多余的right之后的内容
    public int removeElement(int[] nums, int val) 
        int left=0;
        int right=nums.length-1;
        while(left<nums.length-1 && right>0 && left<=right)
            if(nums[left]!=val) left++;
            if(nums[right]==val) right--;
            nums[left]=nums[right];
        
        return left+1;
    
    */
    public int removeElement(int[] A, int elem) 
        int len = A.length;
        for (int i = 0 ; i< len; ++i)
            while (A[i]==elem && i< len) 
                A[i]=A[--len];
            
        
        return len;