Skip to content
Related Articles

Related Articles

Find K such that |A – K| = |B – K|

Improve Article
Save Article
Like Article
  • Last Updated : 07 Mar, 2022

Given two integers A and B where (A ≠ B). The task is to find K such that |A – K| = |B – K|. If no such K exists then print -1.

Examples: 

Input: A = 2, B = 16 
Output:
|2 – 9| = |16 – 9| = 7

Input: A = 5, B = 2 
Output: -1 
 

Approach: It is given that A ≠ B. So let A < B then there are three cases:  

  • K < A: This gives A – K = B – K which gives A = B which is false.
  • K > B: This gives K – A = K – B which is also false.
  • A ≤ K ≤ B: This gives K – A = B – K which gives 2 * K = A + B

If A + B is odd, there is thus no solution. If A + B is even then the answer is (A + B) / 2.

Below is the implementation of the above approach:  

C++




// C++ implementation of the approach
#include <bits/stdc++.h>
using namespace std;
 
// Function to find k such that
// |a - k| = |b - k|
int find_k(int a, int b)
{
    // If (a + b) is even
    if ((a + b) % 2 == 0)
        return ((a + b) / 2);
 
    return -1;
}
 
// Driver code
int main()
{
    int a = 2, b = 16;
 
    cout << find_k(a, b);
 
    return 0;
}


Java




// Java implementation of the approach
class GFG
{
     
// Function to find k such that
// |a - k| = |b - k|
static int find_k(int a, int b)
{
    // If (a + b) is even
    if ((a + b) % 2 == 0)
        return ((a + b) / 2);
 
    return -1;
}
 
// Driver code
public static void main(String[] args)
{
    int a = 2, b = 16;
 
    System.out.println(find_k(a, b));
}
}
 
// This code is contributed by Code_Mech


Python3




# Python3 implementation of the approach
 
# Function to find k such that
# |a - k| = |b - k|
def find_k(a, b) :
 
    # If (a + b) is even
    if ((a + b) % 2 == 0) :
        return ((a + b) // 2);
 
    return -1;
 
# Driver code
if __name__ == "__main__" :
 
    a = 2; b = 16;
 
    print(find_k(a, b));
 
# This code is contributed by AnkitRai01


C#




// C# implementation of the approach
using System;
 
class GFG
{
     
// Function to find k such that
// |a - k| = |b - k|
static int find_k(int a, int b)
{
    // If (a + b) is even
    if ((a + b) % 2 == 0)
        return ((a + b) / 2);
 
    return -1;
}
 
// Driver code
public static void Main()
{
    int a = 2, b = 16;
 
    Console.Write(find_k(a, b));
}
}
 
// This code is contributed by chitranayal


Javascript




<script>
 
// Javascript implementation of the approach
 
// Function to find k such that
// |a - k| = |b - k|
function find_k(a, b)
{
     
    // If (a + b) is even
    if ((a + b) % 2 == 0)
        return ((a + b) / 2);
 
    return -1;
}
 
// Driver code
var a = 2, b = 16;
 
document.write( find_k(a, b));
 
// This code is contributed by akshitsaxenaa09
 
</script>


Output

9

Time Complexity: O(1)

Auxiliary Space: O(1)


My Personal Notes arrow_drop_up
Recommended Articles
Page :

Start Your Coding Journey Now!