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Check if an array can be converted to another given array by swapping pairs of unequal elements
  • Last Updated : 26 Feb, 2021
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Given two arrays arr1[] and arr2[] of size N, consisting of binary integers, the task is to check if arr1[] can be converted to arr2[] by swapping any pair of array elements (arr1[i], arr1[j]) such that i < j and arr1[i] is 1 and arr1[j] is 0 (any number of times). If it is possible to do so, then print “Yes”. Otherwise, print “No”.

Examples:

Input: arr1[] = {0, 1, 1, 0}, arr2[] = {0, 0 1, 1}
Output: Yes
Explanation:
The array arr1[] can be made equal to arr2[] by swapping arr1[1] and arr1[3].

Input: arr1[] = {1, 0, 1}, arr2[] = {0, 1, 0}
Output: No

Approach: The idea to solve this problem is based on the following observations: 



  • The operation doesn’t change the frequency of the number of ones and zeros in array arr1[], so if the number of 0s or 1s are different among arrays, they can never become equal with the above operation.
  • If some prefix of arr2[] contains more 1s than the prefix of arr1[] of the same length, then it is not possible to make arr1[] and arr2[] equal, since 1 can be shifted to right only.
  • Otherwise, in all other cases, arrays can be made equal.

Follow the below steps to solve the problem:

  • Initialize a variable, say count with 0, to store the differences of the prefix sum of arr1[] and arr2[].
  • Count the number of 1s and 0s in both arrays and check if the number of 1s and 0s in arr1[] is not equal to the number of 1s and 0s in arr2[] and then print “No”.
  • Iterate over the range [1, N – 1] using the variable i and do the following:
    • Add the value (arr1[i] – arr2[i]) to the variable count.
    • If the value of count is less than 0, then print “No” else continue for the next pair of elements.
  • After completing the above steps, if the count isn’t negative at any step then print “Yes”.

Below is the implementation of the above approach:

C++




// C++ program for the above approach
 
#include <bits/stdc++.h>
using namespace std;
 
// Function to check if arr1[] can be
// converted to arr2[] by swapping pair
// (i, j) such that i < j and arr[i] is
// 1 and arr[j] is 0
void canMakeEqual(int arr1[], int arr2[], int N)
{
    // Stores the differences of prefix
    // sum of arr1 and arr2
    int count = 0;
 
    // Stores the count of 1 and
    // zero of arr1
    int arr1_one = 0, arr1_zero = 0;
 
    // Stores the count of 1 and
    // zero of arr2
    int arr2_one = 0, arr2_zero = 0;
 
    // Iterate in the range [0, N - 1]
    for (int i = 0; i < N; i++) {
 
        // If arr1[i] is 1, then
        // increment arr1_one by one
        if (arr1[i] == 1) {
            arr1_one++;
        }
 
        // Otherwise increment
        // arr1_zero by one
        else if (arr1[i] == 0) {
            arr1_zero++;
        }
 
        // If arr2[i] is 1, then
        // increment arr2_one by one
        if (arr2[i] == 1) {
            arr2_one++;
        }
 
        // Otherwise increment
        // arr2_zero by one
        else if (arr2[i] == 0) {
            arr2_zero++;
        }
    }
 
    // Check if number of 1s and 0s
    // of arr1 is equal to number of
    // 1s and 0s of arr2 respectievly
    if (arr1_one != arr2_one || arr1_zero != arr2_zero) {
        cout << "No";
        return;
    }
 
    // Iterate over the range [0, N-1]
    for (int i = 0; i < N; i++) {
 
        // Increment count by differences
        // arr1[i] and arr2[i]
        count = count + (arr1[i] - arr2[i]);
 
        // Check if number of 1's in
        // arr2 are more than arr1 and
        // then print "No"
        if (count < 0) {
            cout << "No";
            return;
        }
    }
 
    // Finally, print "Yes"
    cout << "Yes";
}
 
// Driver Code
int main()
{
    // Given input arrays
    int arr1[] = { 0, 1, 1, 0 };
    int arr2[] = { 0, 0, 1, 1 };
 
    // Size of the array
    int N = sizeof(arr1) / sizeof(arr1[0]);
 
    // Function Call
    canMakeEqual(arr1, arr2, N);
 
    return 0;
}

Java




// Java program for the above approach
import java.util.*;
class GFG
{
 
  // Function to check if arr1[] can be
  // converted to arr2[] by swapping pair
  // (i, j) such that i < j and arr[i] is
  // 1 and arr[j] is 0
  static void canMakeEqual(int []arr1, int []arr2, int N)
  {
 
    // Stores the differences of prefix
    // sum of arr1 and arr2
    int count = 0;
 
    // Stores the count of 1 and
    // zero of arr1
    int arr1_one = 0, arr1_zero = 0;
 
    // Stores the count of 1 and
    // zero of arr2
    int arr2_one = 0, arr2_zero = 0;
 
    // Iterate in the range [0, N - 1]
    for (int i = 0; i < N; i++) {
 
      // If arr1[i] is 1, then
      // increment arr1_one by one
      if (arr1[i] == 1) {
        arr1_one++;
      }
 
      // Otherwise increment
      // arr1_zero by one
      else if (arr1[i] == 0) {
        arr1_zero++;
      }
 
      // If arr2[i] is 1, then
      // increment arr2_one by one
      if (arr2[i] == 1) {
        arr2_one++;
      }
 
      // Otherwise increment
      // arr2_zero by one
      else if (arr2[i] == 0) {
        arr2_zero++;
      }
    }
 
    // Check if number of 1s and 0s
    // of arr1 is equal to number of
    // 1s and 0s of arr2 respectievly
    if (arr1_one != arr2_one || arr1_zero != arr2_zero) {
      System.out.print("No");
      return;
    }
 
    // Iterate over the range [0, N-1]
    for (int i = 0; i < N; i++) {
 
      // Increment count by differences
      // arr1[i] and arr2[i]
      count = count + (arr1[i] - arr2[i]);
 
      // Check if number of 1's in
      // arr2 are more than arr1 and
      // then print "No"
      if (count < 0) {
        System.out.print("No");
        return;
      }
    }
 
    // Finally, print "Yes"
    System.out.print("Yes");
  }
 
// Driver Code
public static void main(String[] args)
{
   
    // Given input arrays
    int []arr1 = { 0, 1, 1, 0 };
    int []arr2 = { 0, 0, 1, 1 };
 
    // Size of the array
    int N = arr1.length;
 
    // Function Call
    canMakeEqual(arr1, arr2, N);
}
}
 
// This code is contributed by code_hunt.

Python3




# Python 3 program for the above approach
 
# Function to check if arr1[] can be
# converted to arr2[] by swapping pair
# (i, j) such that i < j and arr[i] is
# 1 and arr[j] is 0
def canMakeEqual(arr1, arr2, N):
   
    # Stores the differences of prefix
    # sum of arr1 and arr2
    count = 0
 
    # Stores the count of 1 and
    # zero of arr1
    arr1_one = 0
    arr1_zero = 0
 
    # Stores the count of 1 and
    # zero of arr2
    arr2_one = 0
    arr2_zero = 0
 
    # Iterate in the range [0, N - 1]
    for i in range(N):
       
        # If arr1[i] is 1, then
        # increment arr1_one by one
        if (arr1[i] == 1):
            arr1_one += 1
 
        # Otherwise increment
        # arr1_zero by one
        elif(arr1[i] == 0):
            arr1_zero += 1
 
        # If arr2[i] is 1, then
        # increment arr2_one by one
        if (arr2[i] == 1):
            arr2_one += 1
 
        # Otherwise increment
        # arr2_zero by one
        elif (arr2[i] == 0):
            arr2_zero += 1
 
    # Check if number of 1s and 0s
    # of arr1 is equal to number of
    # 1s and 0s of arr2 respectievly
    if (arr1_one != arr2_one or arr1_zero != arr2_zero):
        print("No")
        return
 
    # Iterate over the range [0, N-1]
    for i in range(N):
 
        # Increment count by differences
        # arr1[i] and arr2[i]
        count = count + (arr1[i] - arr2[i])
 
        # Check if number of 1's in
        # arr2 are more than arr1 and
        # then print "No"
        if (count < 0):
            print("No")
            return
 
    # Finally, print "Yes"
    print("Yes")
 
# Driver Code
if __name__ == '__main__':
   
    # Given input a
    arr1 =  [0, 1, 1, 0]
    arr2 =  [0, 0, 1, 1]
 
    # Size of the array
    N = len(arr1)
     
    # Function Call
    canMakeEqual(arr1, arr2, N)
     
    # This code is contributed by ipg2016107.

C#




// C# program for the above approach
using System;
using System.Collections.Generic;
 
class GFG{
 
  // Function to check if arr1[] can be
  // converted to arr2[] by swapping pair
  // (i, j) such that i < j and arr[i] is
  // 1 and arr[j] is 0
  static void canMakeEqual(int []arr1, int []arr2, int N)
  {
 
    // Stores the differences of prefix
    // sum of arr1 and arr2
    int count = 0;
 
    // Stores the count of 1 and
    // zero of arr1
    int arr1_one = 0, arr1_zero = 0;
 
    // Stores the count of 1 and
    // zero of arr2
    int arr2_one = 0, arr2_zero = 0;
 
    // Iterate in the range [0, N - 1]
    for (int i = 0; i < N; i++) {
 
      // If arr1[i] is 1, then
      // increment arr1_one by one
      if (arr1[i] == 1) {
        arr1_one++;
      }
 
      // Otherwise increment
      // arr1_zero by one
      else if (arr1[i] == 0) {
        arr1_zero++;
      }
 
      // If arr2[i] is 1, then
      // increment arr2_one by one
      if (arr2[i] == 1) {
        arr2_one++;
      }
 
      // Otherwise increment
      // arr2_zero by one
      else if (arr2[i] == 0) {
        arr2_zero++;
      }
    }
 
    // Check if number of 1s and 0s
    // of arr1 is equal to number of
    // 1s and 0s of arr2 respectievly
    if (arr1_one != arr2_one || arr1_zero != arr2_zero) {
      Console.WriteLine("No");
      return;
    }
 
    // Iterate over the range [0, N-1]
    for (int i = 0; i < N; i++) {
 
      // Increment count by differences
      // arr1[i] and arr2[i]
      count = count + (arr1[i] - arr2[i]);
 
      // Check if number of 1's in
      // arr2 are more than arr1 and
      // then print "No"
      if (count < 0) {
        Console.WriteLine("No");
        return;
      }
    }
 
    // Finally, print "Yes"
    Console.WriteLine("Yes");
  }
 
  // Driver Code
  public static void Main()
  {
 
    // Given input arrays
    int []arr1 = { 0, 1, 1, 0 };
    int []arr2 = { 0, 0, 1, 1 };
 
    // Size of the array
    int N = arr1.Length;
 
    // Function Call
    canMakeEqual(arr1, arr2, N);
  }
 
}
 
// This code is contributed by bgangwar59.

 
 

Output: 
Yes

 

Time Complexity: O(N)
Auxiliary Space: O(1) 

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