文章目录
题目顺序：代码随想录算法公开课，b站上有相应视频讲解
一、题目
977. Squares of a Sorted Array
Given an integer array nums sorted in non-decreasing order, return an array of the squares of each number sorted in non-decreasing order.
Example 1:
Input: nums = [-4,-1,0,3,10]
Output: [0,1,9,16,100]
Explanation: After squaring, the array becomes [16,1,0,9,100].
After sorting, it becomes [0,1,9,16,100].
Example 2:
Input: nums = [-7,-3,2,3,11]
Output: [4,9,9,49,121]
Constraints:
1 <= nums.length <= 104
-104 <= nums[i] <= 104
nums is sorted in non-decreasing order.
Follow up: Squaring each element and sorting the new array is very trivial, could you find an O(n) solution using a different approach?
题目来源： leetcode
二、题解
排序写法
cpp
class Solution {
public:
vector<int> sortedSquares(vector<int>& nums) {
int n = nums.size();
for(int i = 0;i < n;i++){
nums[i] = nums[i] * nums[i];
}
sort(nums.begin(),nums.end());
return nums;
}
};双指针写法
cpp
class Solution {
public:
vector<int> sortedSquares(vector<int>& nums) {
int n = nums.size();
vector<int> res(n,0);
int index = n - 1;
for(int i = 0,j = n - 1;i <= j;){
if(nums[i] * nums[i] > nums[j] * nums[j]){
res[index--] = nums[i] *nums[i];
i++;
}
else{
res[index--] = nums[j] * nums[j];
j--;
}
}
return res;
}
};