CareerCup

Most of the answers above are based on Hashtables. I tried the solution with sorting and merge operations.

static List<Integer> intersect(int[] a, int[] b) {
	Arrays.sort(a);
	Arrays.sort(b);
	
	int N = a.length;
	int M = b.length;
	
	int aPos = 0;
	int bPos = 0;
	
	List<Integer> result = new ArrayList<Integer>();
	while(aPos < N && bPos < M) {
		
		if(a[aPos] == b[bPos]) {
			
			// if Duplicates...
			if(result.size() == 0 || result.get(result.size() - 1) != a[aPos])
				result.add(a[aPos]);
			
			++aPos;
			++bPos;
		}
		
		else if(a[aPos] < b[bPos]) ++aPos;
		else if(a[aPos] > b[bPos]) ++bPos;
		
	}
	
	return result;
}

package careerCup;

import java.util.HashSet;
import java.util.Set;

/* problem Statement: find out common element in two arrays*/

public class CommonElement {
	public static void main(String[] args){
		int[] myfirstArray={4,1,2,3,4,5};
		int[] mySecondArray={4,5,7,1,8,9};
		Set<Integer> s=new HashSet<Integer>();
		//System.out.println("common elements are: ");
		for(int i=0;i<myfirstArray.length;i++){
			for(int j=0;j<mySecondArray.length;j++)
				if(myfirstArray[i]==mySecondArray[j]){
					//System.out.print( myfirstArray[i]+" ");
					s.add(myfirstArray[i]);
					
				}
			
		}
		System.out.println(s);
		
		
	}

}

<?php


$arr1 = array(9,2,10,4,11,6,7,8,1);
$arr2 = array(12,14,6,8,11);

print_r(intersect($arr1, $arr2));

function intersect($arr1, $arr2){
  
  sort($arr1);
  sort($arr2);
  
  foreach ($arr1 as $value1) {
    foreach ($arr2 as $value2) {
       if ($value1 == $value2) {
         $result[] = $value1;
         break;
       }else if ($value1 < $value2) {
         break;
       }
     } 
  }
  return $result;
}

?>

string GetCommonElements(char* array1,char* array2,unsigned length1,unsigned length2)
{
if(!array1 || !array2 || length1<=0 || length2<=0){
return "";
}

char v_char[256];

for(int i=0;i<256;++i){
v_char[i]=0;
}

for(int i=0;i<length1;++i){
v_char[array1[i]]++;
}

string str_ret;
for(int i=0;i<length2;++i){
if(v_char[array2[i]]!=0){
str_ret.push_back(array2[i]);
}
}
return str_ret;
}

import java.util.*;
public class Common
{
 public static void func(int [] array1,int[] array2)
 {
  HashSet<Integer> al=new HashSet<Integer>();
  HashSet<Integer> all=new HashSet<Integer>();
  for (int i:array1)
  {
   al.add(i);
  }
  for (int j:array2)
  {
   all.add(j);
  }
  
  al.retainAll(all);
  System.out.println(al);
 }
public static void main(String args[])
{
 int[] array1={1,2,3,4,3,2,1,2,3,4,5,6,4,3,2};
 int[] array2={4,7,6,5,4,5,6,7,5,5,8,9,0};
 func(array1,array2);
 
}
}

We can do it with O(m) where m>n, m and n being 
the number of elements in two arrays.

/** SUFFICIENT_SIZE is just an assumption, we need 
to re-size the array based on some condition and 
re-Hash the table after re-sizing. For now please 
ignore this and assume that the SUFFICIENT_SIZE is 
just sufficient to accommodate the  elements.*/


{
	int maxCount = (m>n) ? m : n;
	Integer[] hashTable = new Integer[SUFFICIENT_SIZE];
	for(int i =0; i<maxCount; i++)
	{
		//Find hashCode for the elements of both the
 array.
		int firstHashCode = hash( firstArray[i] );
		int secondHashCode = hash( secondArray[i] );

		//Find hash table index for elements of both the array.
		int firstHashTableIndex = findIndex( firstHashCode );
		int secondHashTableIndex = findIndex( secondHashCode );
		
		//Add the elements in the hashTable, if there 
is a collision and the equals method finds the same 
element at that index, we have found the common 
element.

		......Code for adding elements to the hashTable follows......

	}
}

public static void main(String[] args) {
// TODO Auto-generated method stub

//ArrayList<Integer> array = new ArrayList<Integer>();
Integer arr[] = { 1,3,2,4,5,4,2 };
Integer arr1[] = { 8,6,7,3,4,1,2 };

HashSet<Integer> hs=new HashSet<Integer>();
hs=(HashSet) compareArray(arr,arr1);
System.out.println(hs);
}
public static Set compareArray(Integer arr1[],Integer arr2[]){
HashSet hs= new HashSet();
for(int ar1:arr1){
System.out.println("Arr1->"+ar1);
for (int ar2: arr2){
System.out.println("Arr2->"+ar2);
if(ar1==ar2){
hs.add(ar1);
}
}
}
return hs;
}

list1=[1,2,3,4,5,6,7,8,9]
list2=[2,4,6,8,10]
dict1={}
list3=[]
for i in list1:
dict1[i]=1
for i in list2:
try:
if dict1[i]==1:
list3+=[i]
except:
continue
print list3