Two strings - using two pointers, sort array first; Not bad if not considering time complexity.

TwoString10.cs

using System;
using System.Collections.Generic;
using System.IO;
class Solution {
    static void Main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution */
        int T = int.Parse(Console.ReadLine());
        for(int i=0; i<T; i++){
            String A = Console.ReadLine();
            String B = Console.ReadLine();
            Boolean flag = false;
            char [] a = A.ToCharArray();
            Array.Sort(a);
            char [] b = B.ToCharArray();
            Array.Sort(b);
            int j=0,k=0;
            while(j<a.Length && k<b.Length){
                if(a[j]==b[k]){
                    flag = true;
                    break;
                }
                else if(a[j]<b[k])
                    j++;
                else
                    k++;
            }
            if(flag)
                Console.WriteLine("YES");
            else
                Console.WriteLine("NO");
        }
    }
}