C programming language provides two types of searching techniques. They are as follows −
- Linear search
- Binary search
Binary Search
- This method can be applied only to sorted list.
- The given list is divided into two equal parts.
- The given key is compared with the middle element of the list.
Here, three situations may occur, which are as follows −
If the middle element matches the key, then the search will end successfully here
If the middle element is greater than the key, then the search will proceed in the left partition.
If the middle element is lower than the key, then the search will proceed in the right partition.
Input (i/p) − Unsorted list of elements, key.
Output (o/p) −
- Success – If key is found
- Unsuccessful – Otherwise
key = 20 mid = (low +high) /2
Program1
Following is the C program to find the minimum element in an array by using binary search −
#include<stdio.h> int main(){ int a[50], n, i, key, flag = 0, low, mid, high; printf("enter the no: of elements:"); scanf ("%d",&n); printf("enter the elements:"); for(i=0; i<n; i++) scanf( "%d", &a[i]); printf("enter a key element:"); scanf ("%d", &key); low = 0; high = n-1; while (low<= high ){ mid = (low + high) /2; if (a[mid] == key){ flag = 1; break; } else{ if (a[mid] > key) high = mid-1; else low = mid+1; } } if (flag == 1) printf ("search is successful"); else printf("search is unsuccessful"); return 0; }
Output
When the above program is executed, it produces the following result −
Run 1: enter the no: of elements:5 enter the elements: 12 34 11 56 67 enter a key element:45 search is unsuccessful Run 2: enter the no: of elements:3 enter the elements: 12 34 56 enter a key element:34 search is successful
Program2
Given below is another C program to find the minimum element in an array by using binary search −
#include<stdio.h> void Bmin(int *a, int i, int n){ int j, temp; temp = a[i]; j = 2 * i; while (j <= n){ if (j < n && a[j+1] > a[j]) j = j + 1; if (temp < a[j]) break; else if (temp >= a[j]){ a[j / 2] = a[j]; j = 2 * j; } } a[j/2] = temp; return; } int binarysearchmin(int *a,int n){ int i; for(i = n/2; i >= 1; i--){ Bmin(a,i,n); } return a[1]; } int main(){ int n, i, x, min; int a[20]; printf("Enter no of elements in an array\n"); scanf("%d", &n); printf("\nEnter %d elements: ", n); for (i = 1; i <= n; i++){ scanf("%d", &a[i]); } min = binarysearchmin(a, n); printf("\minimum element in an array is : %d", min); return 0; }
Output
When the above program is executed, it produces the following result −
Enter no of elements in an array 5 Enter 5 elements: 12 23 34 45 56 minimum element in an array is: 12