binary search c++ code example

Example 1: how to do binary search in c++ using STL

// BY shivam kumar KIIT
#include<bits/stdc++.h>
usind namespace std;
int main()
{
	int arr[]={10,2,34,2,5,4,1};
  	sort(arr,arr+7);//sort array in ascending order before using binary search
  	binary_search(arr,arr+7,10);//return 1 as element is found
  	binary_search(arr,arr+7,3);//return 0 as element is not found
  	return 0;
}

Example 2: binary search in c++

#include<iostream> 
using namespace std; 
int binarySearch(int arr[], int p, int r, int num) { 
   if (p <= r) { 
      int mid = (p + r)/2; 
      if (arr[mid] == num)   
         return mid ; 
      if (arr[mid] > num)  
         return binarySearch(arr, p, mid-1, num);            
      if (arr[mid] < num)
         return binarySearch(arr, mid+1, r, num); 
   } 
   return -1; 
} 
int main(void) { 
   int arr[] = {1, 3, 7, 15, 18, 20, 25, 33, 36, 40}; 
   int n = sizeof(arr)/ sizeof(arr[0]); 
   int num = 33; 
   int index = binarySearch (arr, 0, n-1, num); 
   if(index == -1)
      cout<< num <<" is not present in the array";
   else
      cout<< num <<" is present at index "<< index <<" in the array"; 
   return 0; 
}

Example 3: c++ binary search

int result = -1;
  int low = 0;
  int high = N-1; // N - # of elements
   while (low <= high)
   {  mid = (low + high) / 2;
      if ( item == vector[mid])
	  {  result = mid;
	     break; 
      }
      else if (item > vector[mid] )
	           { low =  mid + 1; }
          else  { high = mid - 1; }
   }