binary_search.cpp

#include <iostream>
#include <cassert>
#include <vector>

using std::vector;

int binary_search(const vector<int> &a, int x, int left, int right) {

  int mid = (left+right)/2;
  if( right >= left ){

    if(a[mid] == x) return mid;
    else if(a[mid] < x)
      binary_search(a, x, mid+1, right);
    else
    {
      binary_search(a, x, left, mid-1);
    }
  }
  else
    return -1;
}

int linear_search(const vector<int> &a, int x) {
  for (size_t i = 0; i < a.size(); ++i) {
    if (a[i] == x) return i;
  }
  return -1;
}

int main() {
  int n;
  std::cin >> n;
  vector<int> a(n);
  for (size_t i = 0; i < a.size(); i++) {
    std::cin >> a[i];
  }
  int m;
  std::cin >> m;
  vector<int> b(m);
  for (int i = 0; i < m; ++i) {
    std::cin >> b[i];
  }
  int l=0,r=(int)a.size()-1;
  for (int i = 0; i < m; ++i) {
    //replace with the call to binary_search when implemented
    std::cout << binary_search(a, b[i], l, r) << ' ';
  }
}