File content as of revision 0:3d12bad4186e:

#include<stdio.h>
#include "mbed.h"
#include "Serial.h"
Serial uart1(USBTX,USBRX); 
/* Function to find the cross over point (the point before
   which elements are smaller than or equal to x and after
   which greater than x)*/
int findCrossOver(int arr[], int low, int high, int x)
{
    // Base cases
  if (arr[high] <= x) // x is greater than all
    return high;
  if (arr[low] > x)  // x is smaller than all
    return low;
    
  // Find the middle point
  int mid = (low + high)/2;  /* low + (high - low)/2 */
 
  /* If x is same as middle element, then return mid */
  if (arr[mid] <= x && arr[mid+1] > x)
    return mid;
 
  /* If x is greater than arr[mid], then either arr[mid + 1]
    is ceiling of x or ceiling lies in arr[mid+1...high] */
  if(arr[mid] < x)
      return findCrossOver(arr, mid+1, high, x);
 
  return findCrossOver(arr, low, mid - 1, x); 
}  

// This function prints k closest elements to x in arr[].
// n is the number of elements in arr[]
void printKclosest(int arr[], int x, int k, int n)
{
    // Find the crossover point
    int l = findCrossOver(arr, 0, n-1, x);
    int r = l+1;   // Right index to search
    int count = 0; // To keep track of count of elements already printed
 
    // If x is present in arr[], then reduce left index
    // Assumption: all elements in arr[] are distinct
    if (arr[l] == x) l--;
 
    // Compare elements on left and right of crossover
    // point to find the k closest elements
    while (l >= 0 && r < n && count < k)
    {
        if (x - arr[l] < arr[r] - x)
            uart1.printf("%d ", arr[l--]);
        else
            uart1.printf("%d ", arr[r++]);
        count++;
    }
 
    // If there are no more elements on right side, then
    // print left elements
    while (count < k && l >= 0)
        uart1.printf("%d ", arr[l--]), count++;
 
    // If there are no more elements on left side, then
    // print right elements
    while (count < k && r < n)
        uart1.printf("%d ", arr[r++]), count++;
}

/* Driver program to check above functions */
int main()
{
   uart1.baud(9600);
   wait(0.1);
   int arr[] ={12, 16, 22, 30, 35, 39, 42,
               45, 48, 50, 53, 55, 56};
   int n = sizeof(arr)/sizeof(arr[0]);
   int x = 35, k = 4;
   printKclosest(arr, x, 4, n);
   while(1)
   {
       wait(0.1);
       uart1.printf("%d \n",printKclosest);
   }
   //return 0;
}