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 C (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>
#include <string.h>
#include <math.h>

#define max 100000

int* sortMaxmin(int*, int);
int* sortMinmax(int*, int);

int main()
{
    int n, i, count=0;
    int d[max];
    
    scanf("%d", &n);
    for (i=0; i<n; i++) {
        scanf("%d", &d[i]);
    }
    
    sortMaxmin(d, n);
    
    printf("%d", d[n/2]-d[n/2-1]);
    
    return 0;
}

int* sortMaxmin(int *a, int b)
{
    int i, j, tmp;
    for(i=0; i<b; i++){
        for (j=i+1; j<b; j++) {
            if(a[i]>a[j]){
                tmp=a[i];
                a[i]=a[j];
                a[j]=tmp;
            }
        }
    }
    return a;
}

int* sortMinmax(int *a, int b)
{
    int i, j, tmp;
    for(i=0; i<b; i++){
        for (j=i+1; j<b; j++) {
            if(a[i]<a[j]){
                tmp=a[i];
                a[i]=a[j];
                a[j]=tmp;
            }
        }
    }
    return a;
}