力扣-977题（Java）-双指针

淩亂°似流年 2023-01-18 06:37 24阅读 0赞

题目链接：[https://leetcode-cn.com/problems/squares-of-a-sorted-array/][https_leetcode-cn.com_problems_squares-of-a-sorted-array]  
题目如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNDY3Njcw_size_16_color_FFFFFF_t_70]

class Solution {
        
        public int[] sortedSquares(int[] nums) {
        
            //题目中数组已是升序排序
            //找出数组中负数和非负数的分界线
            //如果全是非负数，则平方后升序；如果全是负数，则平方后为倒序
            int len=nums.length;
            int pos=-1;
            
            for(int i=0;i<len;i++)
            if(nums[i]<0) pos=i;
            else break;
    
            int[] array=new int[len];
            int pos1=pos,pos2=pos+1;//第一部分：0~pos1 第二部分：pos2~len-1
    
            for(int i=0;i<len;i++)
            nums[i]=nums[i]*nums[i];
            if(pos==-1) return nums;//全为正数
    
            int j=0;
            while(pos1>=0&&pos2<len){
        
                if(nums[pos1]>nums[pos2]) array[j++]=nums[pos2++];
                else if(nums[pos1]<nums[pos2]) array[j++]=nums[pos1--];
                else {
        array[j++]=nums[pos1--];array[j++]=nums[pos2++];}
            }
            
            while(pos1>=0) array[j++]=nums[pos1--];
            while(pos2<len) array[j++]=nums[pos2++]; 
    
            return array;
    
        }
    }

[https_leetcode-cn.com_problems_squares-of-a-sorted-array]: https://leetcode-cn.com/problems/squares-of-a-sorted-array/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNDY3Njcw_size_16_color_FFFFFF_t_70]: /images/20221021/c09027b2991649d2a3797da09ad24212.png