Squares of a Sorted Array Solutions in C++

// Source : https://leetcode.com/problems/squares-of-a-sorted-array/
// Author : Hao Chen
// Date   : 2019-03-26



class Solution {
public:
    vector<int> sortedSquares(vector<int>& A) {
        // find the place, negative numbers are right, positive number are right.
        // two pointer, one goes left, another goes right.

        //using binary search algorithm
        const int len = A.size();
        int low = 0, high = len- 1;
        int mid =0;
        while (low <= high) {
            mid = low + (high - low)/2;
            if (A[mid] >= 0 ) high = mid - 1;
            if (A[mid] < 0 ) low = mid + 1;
        }

        //TRICKY: make sure  A[mid] <= 0 or A[mid] is A[0]
        if (A[mid] > 0 && mid > 0 ) mid--;
        //cout << mid << " - "<< A[mid]<<  endl;

        vector<int> result;
        low = mid; high = mid+1;
        while ( low >=0 && high < len ) {
            if ( abs(A[low]) < abs(A[high]) ) {
                result.push_back(A[low] * A[low]);
                low --;
            }else {
                result.push_back(A[high] * A[high]);
                high++;
            }
        }

        for (;low >= 0; low--) result.push_back(A[low] * A[low]);
        for (;high<len; high++) result.push_back(A[high] * A[high] );

        return result;
    }
};

/// Source : https://leetcode.com/problems/squares-of-a-sorted-array/
/// Author : liuyubobobo
/// Time   : 2019-01-19

#include <iostream>
#include <vector>

using namespace std;


/// Sorting
/// Time Complexity: O(nlogn)
/// Space Complexity: O(1)
class Solution {
public:
    vector<int> sortedSquares(vector<int>& A) {

        for(int& e: A)
            e = e * e;
        sort(A.begin(), A.end());
        return A;
    }
};


int main() {

    return 0;
}

/// Source : https://leetcode.com/problems/squares-of-a-sorted-array/
/// Author : liuyubobobo
/// Time   : 2019-01-20

#include <iostream>
#include <vector>

using namespace std;


/// Two Pointers
/// Time Complexity: O(n)
/// Space Complexity: O(n)
class Solution {
public:
    vector<int> sortedSquares(vector<int>& A) {

        int n = A.size(), i = 0, j = n -1;
        vector<int> ret;
        while(i <= j)
            if(abs(A[i]) > abs(A[j]))
                ret.push_back(A[i] * A[i]), i ++;
            else
                ret.push_back(A[j] * A[j]), j --;
        reverse(ret.begin(), ret.end());
        return ret;
    }
};


int main() {

    return 0;
}