Generate an array B[] from the given array A[] which satisfies the given conditions

Given an array A[] of N integers such that A[0] + A[1] + A[2] + … A[N – 1] = 0. The task is to generate an array B[] such that B[i] is either ⌊A[i] / 2⌋ or ⌈A[i] / 2⌉ for all valid i and B[0] + B[1] + B[2] + … + B[N – 1] = 0.

Examples:

Input: A[] = {1, 2, -5, 3, -1}
Output: 0 1 -2 1 0

Input: A[] = {3, -5, -7, 9, 2, -2}
Output: 1 -2 -4 5 1 -1

Approach: For even integers, it is safe to assume that B[i] will be A[i] / 2 but for odd integers, to maintain the sum equal to zero, take the ceil of exactly half of odd integers and floor of exactly other half odd integers. Since Odd – Odd = Even and Even – Even = Even and 0 is also Even, it can be said that A[] will always contain even number of odd integers so that the sum can be 0. So for a valid input, there will always be an answer.



Below is the implementation of the above approach:

C++

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// C++ implementation of the approach
#include <bits/stdc++.h>
using namespace std;
  
// Utility function to print
// the array elements
void printArr(int arr[], int n)
{
    for (int i = 0; i < n; i++)
        cout << arr[i] << " ";
}
  
// Function to generate and print
// the required array
void generateArr(int arr[], int n)
{
  
    // To switch the ceil and floor
    // function alternatively
    bool flip = true;
  
    // For every element of the array
    for (int i = 0; i < n; i++) {
  
        // If the number is odd then print the ceil
        // or floor value after division by 2
        if (arr[i] & 1) {
  
            // Use the ceil and floor alternatively
            if (flip ^= true)
                cout << ceil((float)(arr[i]) / 2.0) << " ";
            else
                cout << floor((float)(arr[i]) / 2.0) << " ";
        }
  
        // If arr[i] is even then it will
        // be completely divisible by 2
        else {
            cout << arr[i] / 2 << " ";
        }
    }
}
  
// Driver code
int main()
{
    int arr[] = { 3, -5, -7, 9, 2, -2 };
    int n = sizeof(arr) / sizeof(int);
  
    generateArr(arr, n);
  
    return 0;
}

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Java














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// Java implementation of the approach 


// Utility function to print 


// the array elements 


import java.util.*; 


import java.lang.*; 


  


class GFG 


{ 


  


static void printArr(int arr[], int n) 


{ 


    for (int i = 0; i < n; i++) 


        System.out.print(arr[i] + " "); 


} 


  


// Function to generate and print 


// the required array 


static void generateArr(int arr[], int n) 


{ 


  


    // To switch the ceil and floor 


    // function alternatively 


    boolean flip = true; 


  


    // For every element of the array 


    for (int i = 0; i < n; i++) 


    { 


  


        // If the number is odd then print the ceil 


        // or floor value after division by 2 


        if ((arr[i] & 1) != 0) 


        { 


  


            // Use the ceil and floor alternatively 


            if (flip ^= true) 


                System.out.print((int)(Math.ceil(arr[i] /  


                                            2.0)) + " "); 


            else


                System.out.print((int)(Math.floor(arr[i] /  


                                            2.0)) + " "); 


        } 


  


        // If arr[i] is even then it will 


        // be completely divisible by 2 


        else


        { 


            System.out.print(arr[i] / 2 +" "); 


        } 


    } 


} 


  


// Driver code 


public static void main(String []args) 


{ 


    int arr[] = { 3, -5, -7, 9, 2, -2 }; 


    int n = arr.length; 


  


    generateArr(arr, n); 


} 


} 


  


// This code is contributed by Surendra_Gangwar 



















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Python3














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# Python3 implementation of the approach 


from math import ceil, floor 


  


# Utility function to print 


# the array elements 


def printArr(arr, n): 


    for i in range(n): 


        print(arr[i], end = " ") 


  


# Function to generate and print 


# the required array 


def generateArr(arr, n): 


  


    # To switch the ceil and floor 


    # function alternatively 


    flip = True


  


    # For every element of the array 


    for i in range(n): 


  


        # If the number is odd then print the ceil 


        # or floor value after division by 2 


        if (arr[i] & 1): 


  


            # Use the ceil and floor alternatively 


            flip ^= True


            if (flip): 


                print(int(ceil((arr[i]) / 2)),  


                                   end = " ") 


            else: 


                print(int(floor((arr[i]) / 2)),  


                                    end = " ") 


  


        # If arr[i] is even then it will 


        # be completely divisible by 2 


        else: 


            print(int(arr[i] / 2), end = " ") 


  


# Driver code 


arr = [3, -5, -7, 9, 2, -2] 


n = len(arr) 


  


generateArr(arr, n) 


  


# This code is contributed by Mohit Kumar 



















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C#














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// C# implementation of the approach 


// Utility function to print 


// the array elements 


using System; 


using System.Collections.Generic; 


  


class GFG 


{ 


  


static void printArr(int []arr, int n) 


{ 


    for (int i = 0; i < n; i++) 


        Console.Write(arr[i] + " "); 


} 


  


// Function to generate and print 


// the required array 


static void generateArr(int []arr, int n) 


{ 


  


    // To switch the ceil and floor 


    // function alternatively 


    bool flip = true; 


  


    // For every element of the array 


    for (int i = 0; i < n; i++) 


    { 


  


        // If the number is odd then print the ceil 


        // or floor value after division by 2 


        if ((arr[i] & 1) != 0) 


        { 


  


            // Use the ceil and floor alternatively 


            if (flip ^= true) 


                Console.Write((int)(Math.Ceiling(arr[i] /  


                                            2.0)) + " "); 


            else


                Console.Write((int)(Math.Floor(arr[i] /  


                                            2.0)) + " "); 


        } 


  


        // If arr[i] is even then it will 


        // be completely divisible by 2 


        else


        { 


            Console.Write(arr[i] / 2 +" "); 


        } 


    } 


} 


  


// Driver code 


public static void Main(String []args) 


{ 


    int []arr = { 3, -5, -7, 9, 2, -2 }; 


    int n = arr.Length; 


  


    generateArr(arr, n); 


} 


} 


  


// This code is contributed by 29AjayKumar 



















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Output:


1 -2 -4 5 1 -1





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