#include <iostream>
using namespace std;

const int MAX_LEN = 100;

int find3(int key, int x[MAX_LEN], int low, int high);
int find(int key, int x[MAX_LEN], int size);
int find2(int key, int x[MAX_LEN], int size);
void printArray(int x[MAX_LEN], int size);

int main(){

  int x[MAX_LEN];
  // Initialize sorted array
  x[0] = 0;
  for(int i = 1; i < MAX_LEN;i++){
    x[i] = x[i-1] + rand()%5;
  }
  printArray(x, MAX_LEN);
  int key;
  cout << "Input key" << endl;
  cin >> key;
  //  int index = find2(key, x, MAX_LEN);// linear/iterative binary search
  int index = find3(key, x, 0, MAX_LEN); // recursive binary search
  if(index < 0){
    cout << "Error: cannot find key: " << key << endl;
  } else {
    cout << "Key: " << key << " index: " << index << endl;
  }
  return 0;
}
// --------
void printArray(int x[MAX_LEN], int size){
  for(int i = 0; i < size; i++){
    cout << x[i] << " " ;
  }
  cout << endl;
}
// --------linear search, does not require sorted array------
int find(int key, int x[MAX_LEN], int size){
  for(int i = 0; i < size; i++){
    cout << i << endl;
    if (key == x[i])
      return i;
  }
  return -1;
}

// --------binary search ------
int find2(int key, int x[MAX_LEN], int size){
  //binary search iterative
  int mid = size/2;
  int low = 0;
  int high = size;
  for(int i = 0; i < size && low < high; i++){
    mid = (high + low)/2;
    if(key == x[mid])
      return mid;
    else if (key < x[mid])
      high = mid;
    else if (key > x[mid])
      low = mid+1;

    cout << mid << " " << low << " " << high << endl;
  }
  return -1;
}

// --------binary search ------
int find3(int key, int x[MAX_LEN], int low, int high){
  // binary search recursive
  int mid = (high + low)/2;
  cout << mid << " " << low << " " << high << endl;
  if(low >= high) 
    return -1;
  if(key == x[mid])
    return mid;
  else if (key < x[mid])
    return find3(key, x, low, mid);
  else if (key > x[mid])
    return find3(key, x, mid+1, high);
}