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Replace all elements by difference of sums of positive and negative numbers after that element

  • Last Updated : 16 Sep, 2021

Given an array of positive and negative elements. The task is to replace every i-th element of the array by the absolute difference of absolute sums of positive and negative elements in the range i+1 to N. That is, find the absolute sum of all positive elements and the absolute sum of all negative elements in the range i+1 to N. Now find the absolute difference of these two sums and replace with the i-th element.

Note: The last element of the updated array will be zero.

Examples: 

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

Input : N = 6,  arr[] = {-3, -4, -2, 5, 1, -2}
Output : arr[] = {2, 2, 4, 1, 2, 0}.

Naive Approach: The naive approach is to run two for loops and for all i-th elements, calculate abs value of the sum of all positive and negative elements with index in the range i+1 to N. Now find the absolute difference of both sums and replace with the i-th element. 
Time complexity of this approach will be O(N2) where N is the number of elements in the array.



Below is the implementation of the above approach:  

C++




// C++ program to implement above approach
 
#include <iostream>
using namespace std;
 
// Function to print the array elements
void printArray(int N, int arr[])
{
    for (int i = 0; i < N; i++)
        cout << arr[i] << " ";
 
    cout << endl;
}
 
// Function to replace all elements with absolute
// difference of absolute sums of positive
// and negative elements
void replacedArray(int N, int arr[])
{
    int pos_sum, neg_sum, i, j, diff;
 
    for (i = 0; i < N; i++) {
        pos_sum = 0;
        neg_sum = 0;
 
        // Calculate absolute sums of positive
        // and negative elements in range i+1 to N
        for (j = i + 1; j < N; j++) {
            if (arr[j] > 0)
                pos_sum += arr[j];
            else
                neg_sum += arr[j];
        }
 
        // calculate difference of both sums
        diff = abs(pos_sum) - abs(neg_sum);
 
        // replace i-th elements with absolute
        // difference
        arr[i] = abs(diff);
    }
}
 
// Driver code
int main()
{
    int N = 5;
    int arr[] = { 1, -1, 2, 3, -2 };
    replacedArray(N, arr);
    printArray(N, arr);
 
    N = 6;
    int arr1[] = { -3, -4, -2, 5, 1, -2 };
    replacedArray(N, arr1);
    printArray(N, arr1);
 
    return 0;
}

Java




// Java program to implement above approach
class GFG
{
     
// Function to print the array elements
static void printArray(int N, int []arr)
{
    for (int i = 0; i < N; i++)
        System.out.print(arr[i] + " ");
 
    System.out.println();
}
 
// Function to replace all elements with
// absolute difference of absolute sums
// of positive and negative elements
static void replacedArray(int N, int []arr)
{
    int pos_sum, neg_sum, i, j, diff;
 
    for (i = 0; i < N; i++)
    {
        pos_sum = 0;
        neg_sum = 0;
 
        // Calculate absolute sums of positive
        // and negative elements in range i+1 to N
        for (j = i + 1; j < N; j++)
        {
            if (arr[j] > 0)
                pos_sum += arr[j];
            else
                neg_sum += arr[j];
        }
 
        // calculate difference of both sums
        diff = Math.abs(pos_sum) - Math.abs(neg_sum);
 
        // replace i-th elements with absolute
        // difference
        arr[i] = Math.abs(diff);
    }
}
 
// Driver code
public static void main(String args[])
{
    int N = 5;
    int []arr = { 1, -1, 2, 3, -2 };
    replacedArray(N, arr);
    printArray(N, arr);
 
    N = 6;
    int []arr1 = { -3, -4, -2, 5, 1, -2 };
    replacedArray(N, arr1);
    printArray(N, arr1);
}
}
 
// This code is contributed by Akanksha Rai

Python3




# Python 3 program to implement
# above approach
 
# Function to print the array elements
def printArray(N, arr):
    for i in range(N):
        print(arr[i], end = " ")
 
    print("\n", end = "")
 
# Function to replace all elements with
# absolute difference of absolute sums
# of positive and negative elements
def replacedArray(N, arr):
    for i in range(N):
        pos_sum = 0
        neg_sum = 0
 
        # Calculate absolute sums of positive
        # and negative elements in range i+1 to N
        for j in range(i + 1, N, 1):
            if (arr[j] > 0):
                pos_sum += arr[j]
            else:
                neg_sum += arr[j]
 
        # calculate difference of both sums
        diff = abs(pos_sum) - abs(neg_sum)
 
        # replace i-th elements with absolute
        # difference
        arr[i] = abs(diff)
 
# Driver code
if __name__ == '__main__':
    N = 5
    arr = [1, -1, 2, 3, -2]
    replacedArray(N, arr)
    printArray(N, arr)
 
    N = 6
    arr1 = [-3, -4, -2, 5, 1, -2]
    replacedArray(N, arr1)
    printArray(N, arr1)
 
# This code is contributed by
# Surendra_Gangwar

C#




// C# program to implement above approach
using System;
 
class GFG
{
     
// Function to print the array elements
static void printArray(int N, int []arr)
{
    for (int i = 0; i < N; i++)
        Console.Write(arr[i] + " ");
 
    Console.WriteLine();
}
 
// Function to replace all elements with
// absolute difference of absolute sums
// of positive and negative elements
static void replacedArray(int N, int []arr)
{
    int pos_sum, neg_sum, i, j, diff;
 
    for (i = 0; i < N; i++)
    {
        pos_sum = 0;
        neg_sum = 0;
 
        // Calculate absolute sums of positive
        // and negative elements in range i+1 to N
        for (j = i + 1; j < N; j++)
        {
            if (arr[j] > 0)
                pos_sum += arr[j];
            else
                neg_sum += arr[j];
        }
 
        // calculate difference of both sums
        diff = Math.Abs(pos_sum) - Math.Abs(neg_sum);
 
        // replace i-th elements with absolute
        // difference
        arr[i] = Math.Abs(diff);
    }
}
 
// Driver code
static void Main()
{
    int N = 5;
    int []arr = { 1, -1, 2, 3, -2 };
    replacedArray(N, arr);
    printArray(N, arr);
 
    N = 6;
    int []arr1 = { -3, -4, -2, 5, 1, -2 };
    replacedArray(N, arr1);
    printArray(N, arr1);
}
}
 
// This code is contributed by mits

Javascript




<script>
 
// Javascript program to implement above approach   
 
// Function to prvar the array elements
function printArray(N, arr)
{
    for(i = 0; i < N; i++)
        document.write(arr[i] + " ");
 
    document.write("<br/>");
}
 
// Function to replace all elements with
// absolute difference of absolute sums
// of positive and negative elements
function replacedArray(N, arr)
{
    var pos_sum, neg_sum, i, j, diff;
 
    for(i = 0; i < N; i++)
    {
        pos_sum = 0;
        neg_sum = 0;
 
        // Calculate absolute sums of positive
        // and negative elements in range i+1 to N
        for(j = i + 1; j < N; j++)
        {
            if (arr[j] > 0)
                pos_sum += arr[j];
            else
                neg_sum += arr[j];
        }
 
        // Calculate difference of both sums
        diff = Math.abs(pos_sum) -
               Math.abs(neg_sum);
 
        // Replace i-th elements with absolute
        // difference
        arr[i] = Math.abs(diff);
    }
}
 
// Driver code
var N = 5;
var arr = [ 1, -1, 2, 3, -2 ];
replacedArray(N, arr);
printArray(N, arr);
 
N = 6;
var arr1 = [ -3, -4, -2, 5, 1, -2 ];
replacedArray(N, arr1);
printArray(N, arr1);
 
// This code is contributed by aashish1995
 
</script>
Output: 
2 3 1 2 0 
2 2 4 1 2 0

 

Efficient Approach: Initialize positive and negative sums as 0. Now run a single for loop from the last element to the first element and calculate diff = abs(pos_sum) – abs(neg_sum). 
Now if the i-th element is positive, add it to pos_sum otherwise add it to neg_sum. After all, replace the i-th element with absolute difference i.e. abs(diff).

Below is the implementation of the above approach:  

C++




// C++ program to implement above approach
 
#include <iostream>
using namespace std;
 
// Function to print the array elements
void printArray(int N, int arr[])
{
    for (int i = 0; i < N; i++)
        cout << arr[i] << " ";
 
    cout << endl;
}
 
// Function to replace all elements with absolute
// difference of absolute sums of positive
// and negative elements
void replacedArray(int N, int arr[])
{
    int pos_sum, neg_sum, i, j, diff;
 
    pos_sum = 0;
    neg_sum = 0;
 
    for (i = N - 1; i >= 0; i--) {
 
        // calculate difference of both sums
        diff = abs(pos_sum) - abs(neg_sum);
 
        // if i-th element is positive,
        // add it to positive sum
        if (arr[i] > 0)
            pos_sum += arr[i];
 
        // if i-th element is negative,
        // add it to negative sum
        else
            neg_sum += arr[i];
 
        // replace i-th elements with
        // absolute difference
        arr[i] = abs(diff);
    }
}
 
// Driver Code
int main()
{
    int N = 5;
    int arr[] = { 1, -1, 2, 3, -2 };
    replacedArray(N, arr);
    printArray(N, arr);
 
    N = 6;
    int arr1[] = { -3, -4, -2, 5, 1, -2 };
    replacedArray(N, arr1);
    printArray(N, arr1);
 
    return 0;
}

Java




// Java program to implement above approach
class GFG
{
     
    // Function to print the array elements
    static void printArray(int N, int arr[])
    {
        for (int i = 0; i < N; i++)
            System.out.print(arr[i] + " ");
     
        System.out.println();
    }
     
    // Function to replace all elements with absolute
    // difference of absolute sums of positive
    // and negative elements
    static void replacedArray(int N, int arr[])
    {
        int pos_sum, neg_sum, i, j, diff;
     
        pos_sum = 0;
        neg_sum = 0;
     
        for (i = N - 1; i >= 0; i--)
        {
     
            // calculate difference of both sums
            diff = Math.abs(pos_sum) - Math.abs(neg_sum);
     
            // if i-th element is positive,
            // add it to positive sum
            if (arr[i] > 0)
                pos_sum += arr[i];
     
            // if i-th element is negative,
            // add it to negative sum
            else
                neg_sum += arr[i];
     
            // replace i-th elements with
            // absolute difference
            arr[i] = Math.abs(diff);
        }
    }
     
    // Driver Code
    public static void main (String[] args)
    {
        int N = 5;
        int arr[] = { 1, -1, 2, 3, -2 };
        replacedArray(N, arr);
        printArray(N, arr);
     
        N = 6;
        int arr1[] = { -3, -4, -2, 5, 1, -2 };
        replacedArray(N, arr1);
        printArray(N, arr1);
    }
}
 
// This code is contributed by ihritik

Python3




# Python program to implement above approach
 
# Function to print the array elements
def printArray(N, arr) :
 
    for i in range (0, N) :
        print(arr[i], end=" ")
 
    print()
 
 
# Function to replace all elements with absolute
# difference of absolute sums of positive
# and negative elements
def replacedArray(N, arr) :
 
     
    pos_sum = 0
    neg_sum = 0
 
    for i in range (N - 1,-1, -1) :
 
        # calculate difference of both sums
        diff = abs(pos_sum) - abs(neg_sum)
 
        # if i-th element is positive,
        # add it to positive sum
        if (arr[i] > 0) :
            pos_sum = pos_sum + arr[i]
 
        # if i-th element is negative,
        # add it to negative sum
        else :
            neg_sum = neg_sum + arr[i]
 
        # replace i-th elements with
        # absolute difference
        arr[i] = abs(diff)
 
# Driver Code
 
N = 5
arr = [ 1, -1, 2, 3, -2 ]
replacedArray(N, arr)
printArray(N, arr)
 
N = 6
arr1 = [ -3, -4, -2, 5, 1, -2 ]
replacedArray(N, arr1)
printArray(N, arr1)
 
# This code is contributed by ihritik

C#




// C# program to implement above approach
using System;
 
class GFG
{
     
    // Function to print the array elements
    static void printArray(int N, int [] arr)
    {
        for (int i = 0; i < N; i++)
            Console.Write(arr[i] + " ");
     
        Console.WriteLine();
    }
     
    // Function to replace all elements with absolute
    // difference of absolute sums of positive
    // and negative elements
    static void replacedArray(int N, int [] arr)
    {
        int pos_sum, neg_sum, i, diff;
     
        pos_sum = 0;
        neg_sum = 0;
     
        for (i = N - 1; i >= 0; i--)
        {
     
            // calculate difference of both sums
            diff = Math.Abs(pos_sum) - Math.Abs(neg_sum);
     
            // if i-th element is positive,
            // add it to positive sum
            if (arr[i] > 0)
                pos_sum += arr[i];
     
            // if i-th element is negative,
            // add it to negative sum
            else
                neg_sum += arr[i];
     
            // replace i-th elements with
            // absolute difference
            arr[i] = Math.Abs(diff);
        }
    }
     
    // Driver Code
    public static void Main ()
    {
        int N = 5;
        int [] arr = { 1, -1, 2, 3, -2 };
        replacedArray(N, arr);
        printArray(N, arr);
     
        N = 6;
        int [] arr1 = { -3, -4, -2, 5, 1, -2 };
        replacedArray(N, arr1);
        printArray(N, arr1);
    }
}
 
// This code is contributed by ihritik

Javascript




<script>
 
 
// Function to print the array elements
function printArray(N,  arr)
{
    for (var i = 0; i < N; i++)
        document.write( arr[i] +" ");
 
    document.write("<br>");
}
 
// Function to replace all elements with absolute
// difference of absolute sums of positive
// and negative elements
function replacedArray( N,  arr)
{
    var pos_sum, neg_sum, i, j, diff;
 
    pos_sum = 0;
    neg_sum = 0;
 
    for (i = N - 1; i >= 0; i--) {
 
        // calculate difference of both sums
        diff = Math.abs(pos_sum) - Math.abs(neg_sum);
 
        // if i-th element is positive,
        // add it to positive sum
        if (arr[i] > 0)
            pos_sum += arr[i];
 
        // if i-th element is negative,
        // add it to negative sum
        else
            neg_sum += arr[i];
 
        // replace i-th elements with
        // absolute difference
        arr[i] = Math.abs(diff);
    }
}
 
// Driver Code
var N = 5;
    var arr = [ 1, -1, 2, 3, -2 ];
    replacedArray(N, arr);
    printArray(N, arr);
    N=6;
var arr1 = [-3, -4, -2, 5, 1, -2 ];
    replacedArray(N, arr1);
    printArray(N, arr1);
 
 
 
 
</script>
Output: 
2 3 1 2 0 
2 2 4 1 2 0

 

Time complexity: O(N), where N is the number of elements.
 




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