Example 1: the function search() returns 1 if query is present
           in the array data[] and 0 otherwise. No assumption 
           is made about data order. Note how getinput() sets 
           the variables when called in main().

#include <iostream>
using namespace std;

int search(int data[], int size, int query) {
  for(a=0;a<size; a++)
    if (data[a] == query) 
      return 1;

  return 0;
}

void getinput(int data[], int& size) {
  cout << "How many elements in the array ?\n";
  cin >> size;

  for(int a=0; a<size; a++)
    cin >> data[a];

  return;
}

int main() {
  int data[100], size;

  getinput(data, size); // we assume nothing about the data order
  if (search(data,0,size-1,10)) 
    cout << "The number 10 is present\n";
  else
    cout << "The number 10 is not present\n";

  return 0;
}



Example 2 : binsearch searches for q in the array a[] using
            the "binary search" algorithm. It assumes that 
            the array a[] is sorted in increasing order. 
            Note the recursive call in the program body.



#include<iostream>
using namespace std;

// binsearch assumes that the array is already sorted

int binsearch(int a[], int low, int high, int q) {
  int mid = (low+high)/2;

  if (low==high) { // termination condition for the recursion
    if (q==a[low])
      return 1;
    else 
      return 0;
  } else if (q==a[mid]) {
    return 1;
  }else if (q>a[mid]) {
    return binsearch(a, mid, high, q);
  }else { // The only remaining possibility is q < a[mid].
    return binsearch(a,low, mid, q);
  }
}

void getinput(int data[], int& size) {
  cout << "How many elements in the array ?\n";
  cin >> size;

  for(int a=0; a<size; a++)
    cin >> data[a];

  return;
}

int main() {
  int data[100], size;

  getinput(data, size); // we assume the array is sorted in increasing order
  if (binsearch(data,0,size-1,10)) 
    cout << "The number 10 is present\n";
  else
    cout << "The number 10 is not present\n";

  return 0;
}