What are some variants of binary search in C++?

What are some variants of binary search in C++?

In C++, binary search can be implemented in several ways. The most common variants include:

1. Standard Binary Search: Finds the exact position of a target value.
2. Lower Bound: Finds the first position where a value can be inserted without violating the order.
3. Upper Bound: Finds the position just after the last occurrence of a value.
4. Count Occurrences: Counts how many times a value appears in a sorted array.
5. Find First and Last Position: Returns the first and last indices of a target value in a sorted array.

Can you show me the code for the standard binary search?

Sure! Here's a simple implementation of the standard binary search in C++:

#include <iostream>
using namespace std;

int binarySearch(int arr[], int size, int target) {
    int left = 0, right = size - 1;
    while (left <= right) {
        int mid = left + (right - left) / 2;
        if (arr[mid] == target) return mid;
        else if (arr[mid] < target) left = mid + 1;
        else right = mid - 1;
    }
    return -1; // Target not found
}

int main() {
    int arr[] = {1, 2, 3, 4, 5};
    int size = sizeof(arr) / sizeof(arr[0]);
    int target = 3;
    int result = binarySearch(arr, size, target);
    if (result != -1) cout << "Element found at index: " << result;
    else cout << "Element not found.";
    return 0;
}

What is the time complexity of binary search?

The time complexity of binary search is O(log n), where n is the number of elements in the array. This is because the search space is halved with each iteration.