BinarySearch.cpp

#include <iostream>
#include <vector>

using namespace std;

int binarySearch(int value, vector<int> &vec, int leftIndex, int rightIndex) {
  int mid = (leftIndex + rightIndex) / 2;

  if (leftIndex <= rightIndex) {
    if (value > vec[mid]) {
      leftIndex = mid + 1;
      return binarySearch(value, vec, leftIndex, rightIndex);
    } else if (value < vec[mid]) {
      rightIndex = mid - 1;
      return binarySearch(value, vec, leftIndex, rightIndex);
    } else {
      return mid;
    }
  } else {
    return -1;
  }
}

int main() {
  vector<int> vec;

  for (int index = 1; index <= 50; index++) {
    vec.push_back(index);
  }

  int value = 45;

  int index = binarySearch(value, vec, 0, vec.size());

  if (index >= 0) {
    cout << "Value " << to_string(value) << " found at position "
         << to_string(index) << endl;
  } else {
    cout << "Could not find the value " << to_string(value) << endl;
  }
}