Program to illustrate Binary Search

Example to illustrate Binary search 

consider an array[10]
Data:       10     18      19     20     25     30     49      57      64    72
Array:    a[0]   a[1]   a[2]   a[3]   a[4]   a[5]   a[6]   a[7]   a[8]  a[9]
search no = 49

Iteration 1: start = 0
                   end= 9
                   middle = (start+end)/2;
                               = 0 + 9 / 2
                               = 4.5 
                               = rounded 4   i.e  a[4]=25

Iteration 2: search no 49 > 25
                   start = middle + 1 = 4 + 1 = 5
                   end= 9
                   middle = (start+end)/2;
                               = 5 + 9 / 2
                               = 7  i.e   a[7]= 57 

Iteration 3: search no 49 < 57
                   start =  5
                   end= middle  - 1 = 7 - 1 = 6
                   middle = (start+end)/2;
                               = 5 + 6 / 2
                               = 5.5
                               = rounded 5  i.e   a[5]= 30 
     
Iteration 4: search no 49 < 30
                   start = middle + 1 = 5 + 1 = 6
                   end= 6
                   middle = (start+end)/2;
                               = 6 + 6 / 2
                               = 6  i.e   a[6]= 49 
                  
Iteration 5: search no 49  is equal to middle no 49 i.e 49 = 49
                   stop.

Program :

// Program to illustrate Binary Search
    #include <stdio.h>
    int main()
    {
      int array[100],start,end, middle , search , flag, i, n;
      printf("Enter number of elements in array\n");
      scanf("%d", &n);
      printf("Enter %d integer(s)\n", n);
      for (i = 0; i < n; i++)
        {
         scanf("%d", &array[i]);
        }
      printf("\n Array elements are :");
      for (i = 0; i < n; i++)
        {
        printf("\n Address.> :%p --> Array : array[%d] Data : %d Location : %d", &array[i],i,array[i],i+1);
        }
      printf("\nEnter a number to search :");
      scanf("%d", &search);
     
      start = 0;
      end = n - 1;
     
    
      while (start <= end)
       {
          middle = (start+end)/2;
          if (search < array[middle])
             end = middle - 1;   
          else if (search  > array[middle])
             start = middle + 1;
          else if(search == array[middle])
            {
             printf("element %d found at location %d.\n", search, middle+1);
             flag=1;
             break;
            }
       }
       if (flag==0)
          printf("Not found! %d isn't present in the list.\n", search);
    
       return 0; 
    }



      output: