Squares of sorted array in O(n) time 

#include <iostream>
using namespace std;

int main() {
    
    int arr[] = {-2, -1, 0, 2, 3};
    int n = sizeof(arr)/sizeof(arr[0]);
    int pos = -1;
    int count = 0;
    
    for(int i=0 ; i<n; i++){
        if(arr[i]>0){
            pos = i;
            count++;
            break;
        }
    }
    
    int sqr[n];
    
    if(pos==-1){
        for(int i=n-1; i>=0; i--){
            sqr[(n-1)-i] = arr[i] * arr[i];
        }
    }
    
    else if(count == n-1){
        for(int i=0; i<n; i++){
            arr[i] = arr[i]*arr[i];
        }
    }else if(pos != -1 && count != n-1){
        
        int j=pos-1;
        int k = 0;
        while(j>=0 && pos<n){
            
            if((arr[j]*arr[j])>(arr[pos]*arr[pos])){
                sqr[k] = arr[pos]*arr[pos];
                pos++;
                k++;
            }else if((arr[pos]*arr[pos])>(arr[j]*arr[j])){
                sqr[k] = arr[j]*arr[j];
                k++;
                j--;
            }else {
                sqr[k] = arr[j]*arr[j];
                k++;
                sqr[k] = arr[pos]*arr[pos];
                pos++;
                j--;
                k++;
            }
            
        }
      
        
        while(j>=0){
            sqr[k] = arr[j]*arr[j];
            j--;
            k++;
        }

        while(pos<=n-1){
            sqr[k] = arr[pos]*arr[pos];
            pos++;
            k++;
        }
        
    }
    
    
    for(int i=0 ; i<n;i++){
        cout<<sqr[i]<<" ";
    }
    
    
}