Example 1: binary search program c++
using namespace std;
// This program performs a binary search through an array, must be sorted to work
int binarySearch(int array[], int size, int value)
{
int first = 0, // First array element
last = size - 1, // Last array element
middle, // Mid point of search
position = -1; // Position of search value
bool found = false; // Flag
while (!found && first <= last)
{
middle = (first + last) / 2; // Calculate mid point
if (array[middle] == value) // If value is found at mid
{
found = true;
position = middle;
}
else if (array[middle] > value) // If value is in lower half
last = middle - 1;
else
first = middle + 1; // If value is in upper half
}
return position;
}
int main ()
{
const int size = 5; // size initialization
int array[size] = {1, 2, 3, 4, 5}; // declare array of size 10
int value; // declare value to be searched for
int result; // declare variable that will be returned after binary search
cout << "What value would you like to search for? "; // prompt user to enter value
cin >> value;
result = binarySearch(array, size, value);
if (result == -1) // if value isn't found display this message
cout << "Not found\n";
else // If value is found, displays message
cout << "Your value is in the array.\n";
return 0;
}
Example 2: how to do binary search in c++ using STL
// BY shivam kumar KIIT
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 3: binary search function in c++
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 4: binary search in c++
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 5: Binary search in c++
//By Sudhanshu Sharan
using namespace std;
// BCT= o(1) and WCT=O(logn) time taken for unsucessful search is always o(logn)
int BinSearch( int arr[],int key,int len)
{
int h,mid,l;
l=0;
h=len-1;
while(l<=h)
{
mid=((l+h)/2);
if(key==arr[mid])
return mid;
else if(key<arr[mid])
h=mid-1;
else
l=mid+1;
}
return -1;
}
int main()
{
int key,i,len;
int arr[] = {1,2,3,6,9,12,15,34,54};
len=sizeof(arr)/sizeof(arr[0]);
cout<<"enter the key to be searched";
cin>>key;
int result= BinSearch(arr,key,len);
(result == -1)
? cout<<"Element is not present in the array"<<endl
: cout<<"Element is present at index : "<<result<<endl;
for(i=0;i<len-1;i++)
cout<<arr[i]<<" ";
return 0;
}
Example 6: c++ binary search
int result = -1;
int low = 0;
int high = N-1; // N -
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; }
}