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.Scanner;

public class Main {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		int first = 0;
		int second = 0;
		char firstChar = 0;
		char secondChar = 0;
		for(int i = 0 ; i < 4 ; i++) {
			char c = s.charAt(i);
			if(firstChar == 0) {
				firstChar = c;
				first++;
			} else if(c != firstChar && secondChar == 0) {
				secondChar = c;
				second++;
			} else if(c == firstChar) {
				first++;
			} else if(c == secondChar) {
				second++;
			}
		}
		if(first == 2 && second == 2) {
			System.out.println("Yes");
		} else {
			System.out.println("No");
		}
		sc.close();

	}

}