How to find the only different number in two unsorted arrays?

Question

Anonymous · Accepted Answer

You can use xor

Anon · Answer

Why not just sum both arrays up the difference will be the different no.

Anonymous · Answer

Using HashTable to count the occurrence of each number

Anonymous · Answer

In Python:

from collections import Counter
def diffNum(a,b):
	aCount = Counter(a)
	for x in b:
		if x not in aCount:
			return x
	return None

a = [1,3,4,5,2]
b = [1,2,7,5,4,3]
print diffNum(a,b)

Anonymous · Answer

Given 2 lists a and b with one element that is different, sum(a) - sum(b) will give you the element

Vb · Answer

Here is the C# code with HashTable

    class Class1
    {
        public int Different_Number(int[] A, int[] B)
        {
            if (A.Length < B.Length)
            {
                return Hash_It(A, B);
            }
            else
            {
                return Hash_It(B, A);
            }

        }

        private int Hash_It(int[] A, int[] B)
        {
            Hashtable ht = new Hashtable();  

            for (int i = 0; i < A.Length; i++)
            {
                ht.Add(A[i], i);
            }

            for (int i = 0; i < B.Length; i++)
            {
                if (!ht.Contains(B[i]))
                {
                    return B[i];
                }
            }
            return null;
        }
        public static void Main()
        {
            int[] A = new int[] { 1,5,3,8};             /* Unsorted array */
            int[] B = new int[] { 5,3,8,2102,1};

            Class1 cls = new Class1();                                  
            Console.WriteLine(cls.Different_Number(A, B));
            Console.ReadLine();
        }
    }

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