左右指针的经典应用

左右下标元素平方相比，大的放新数组右边，比较简单，不赘述

class Solution {
public:
vector<int> sortedSquares(vector<int> &nums) {
	int len = nums.size();
    vector<int> res(len, 0);
    int j = len - 1;
    int left = 0;
    int right = len - 1;
    while (left <= right) {
        int leftValue = pow(nums[left], 2);
        int rightValue = pow(nums[right], 2);
        if (leftValue < rightValue) {
            res[j--] = rightValue;
            right--;
        } else {
            res[j--] = leftValue;
            left++;
        }
    }
    return res;
}
};