Position of a person diametrically opposite on a circle

There are n people standing on the circumference of a circle. Given the position of a person m, the task is to find the position of the person standing diametrically opposite to m on the circle. 

Examples:

Input: n = 6, m = 2 
Output: 5 
Position 5 is opposite to 2 when there are 6 positions in total

Input: n = 8, m = 5 
Output: 1 

Approach: There are two cases: 

• If m > n / 2 then answer will always be m – (n / 2).
• If m ? n / 2 then answer will always be m + (n / 2).

Below is the implementation of the above approach:  

C++

// C++ implementation of the approach
#include <bits/stdc++.h>
using namespace std;

// Function to return the required position
int getPosition(int n, int m)
{
    if (m > (n / 2))
        return (m - (n / 2));

    return (m + (n / 2));
}

// Driver code
int main()
{
    int n = 8, m = 5;
    cout << getPosition(n, m);

    return 0;
}

Java

// Java implementation of the approach
class Sol
{

// Function to return the required position
static int getPosition(int n, int m)
{
    if (m > (n / 2))
        return (m - (n / 2));

    return (m + (n / 2));
}

// Driver code
public static void main(String args[])
{
    int n = 8, m = 5;
    System.out.println(getPosition(n, m));

}
}
// This code is contributed by Arnab Kundu

Python3

# Python3 implementation of the approach

# Function to return the
# required position
def getPosition(n, m):

    if (m > (n // 2)) :
        return (m - (n // 2))

    return (m + (n // 2))

# Driver code
n = 8
m = 5
print(getPosition(n, m))

# This code is contributed
# by ihritik

C#

// C# implementation of the approach
using System;

class GFG
{

// Function to return the required position
static int getPosition(int n, int m)
{
    if (m > (n / 2))
        return (m - (n / 2));

    return (m + (n / 2));
}

    // Driver code
    static public void Main ()
    {

    int n = 8, m = 5;
    Console.WriteLine(getPosition(n, m));
    }
}

// This code is contributed by ajit.

PHP

<?php
// PHP implementation of the approach

// Function to return the
// required position
function getPosition($n, $m)
{

    if ($m > ($n / 2))
        return ($m - ($n / 2));

    return ($m + ($n / 2));
}

// Driver code
$n = 8;
$m = 5;
echo getPosition($n, $m);

// This code is contributed
// by ihritik
?>

Javascript

<script>

// Javascript implementation of the approach

// Function to return the required position
function getPosition( n, m)
{
    if (m > (n / 2))
        return (m - parseInt(n / 2));

    return (m + parseInt(n / 2));
}

// Driver code
var n = 8, m = 5;
document.write(getPosition(n, m));

</script>

Output:

1

Time Complexity: O(1), as we are not using any loops.

Auxiliary Space: O(1), as we are not using any extra space.