977 square of a sorted array

977.有序数组的平方

cpp：

错误代码1：

class Solution {
public:
    vector<int> sortedSquares(vector<int>& nums)
    {
        int i = 0;

        while (i < nums.size())
        {
            nums[i] = nums[i] * nums[i]; //溢出越界了
        }

        int right = 0, left = 1;

        while (right < left < nums.size())
        {
            if (nums[right] > nums[left])
            {
                nums[left] = nums[right];
            }

            right++, left++;
        }

        return nums;
    }
};

错误代码2：

    class Solution {
    public:
        vector<int> sortedSquares(vector<int>& nums)
        {
            int i = 0;
            int j = nums.size() - 1;
    
            while (i <= j)
            {
                if (nums[i] * nums[i] > nums[j] * nums[j])
                {
                    nums[i] = nums[j] * nums [j]; //导致数据覆盖问题，且没有排序
                }
                i++, j--;
            }
    
            return nums;
        }
    };

错误代码3：

    class Solution {
    public:
        vector<int> sortedSquares(vector<int>& nums)
        {
            int left = 0, index = 0; //要从后往前排
            int right = nums.size() - 1;
            vector<int> result(nums.size());
    
            while (left <= right)
            {
                if (nums[left] * nums[left] > nums[right] * nums[right])
                {
                    result[index] = nums[right] * nums [right];
                    right--;
                }
                else
                {
                    result[index] = nums[left] * nums[left];
                    left++;
                }
    
                index++;
            }
    
            return result;
        }
    };

正确代码：

class Solution {
public:
    vector<int> sortedSquares(vector<int>& nums)
    {
        int left = 0;
        int right = nums.size() - 1;
        int index = nums.size() - 1; //从后往前排
        vector<int> result(nums.size());

        while (left <= right)
        {
            if (nums[left] * nums[left] > nums[right] * nums[right])
            {
                result[index] = nums[left] * nums [left];
                left++;
            }
            else
            {
                result[index] = nums[right] * nums[right];
                right--;
            }

            index--; //别忘了移动index，每次循环肯定都会给新数组赋过值的
        }

        return result;
    }
};

go：

func sortedSquares(nums []int) []int {
    left := 0
    right := len(nums) - 1
    index := len(nums) - 1
    results := make([]int, len(nums), len(nums))
    
    for left <= right {
        if nums[left] * nums[left] > nums[right] * nums[right] {
            results[index] = nums[left] * nums[left]
            left++
        } else {
            results[index] = nums[right] * nums[right]
            right--
        }

        index--
    }
    
    return results
}