Problem:
Score : 100 points

Problem Statement

You are given a 4-character string S consisting of uppercase English letters.
Determine if S consists of exactly two kinds of characters which both appear twice in S.

Constraints

The length of S is 4.

S consists of uppercase English letters.

Input

Input is given from Standard Input in the following format:

S

Output

If S consists of exactly two kinds of characters which both appear twice in S, print Yes; otherwise, print No.

Sample Input 1

ASSA

Sample Output 1

Yes

S consists of A and S which both appear twice in S.

Sample Input 2

STOP

Sample Output 2

No

Sample Input 3

FFEE

Sample Output 3

Yes

Sample Input 4

FREE

Sample Output 4

No

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Scanner;

public class Main { 
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String line = sc.nextLine();
		
		HashMap<Character,Integer> resultMap = new HashMap();
		for(int i = 0;i<line.length();i++) {
			Character tmp = line.charAt(i);
			if(resultMap.containsKey(tmp)) {
				resultMap.put(tmp, resultMap.get(tmp)+1);
			}else {
				resultMap.put(tmp, 0);
			}
		}
		
		String strResult = "No";

		if(resultMap.size() == 2) {
			 for(Integer t:resultMap.values()) {
				 if(resultMap.containsValue(t)) {
					 strResult = "Yes";
				 }
			 }
		}
		System.out.println(strResult);
		
	}
}