Q10008: What's Cryptanalysis

// Run time: 0.000
#include <stdio.h>
#include <ctype.h>
#define N 26
int arr[N];
bool state[N];
void calculate(char ch);
void sort();
int select();

int main()
{
    char ch;
    int n;
    int i;
    bool s = true;
    scanf("%d\n", &n);
    while (n--)
    {
        while (true)
        {
            if ((ch = getchar()) == '\n')
                break;
            calculate(ch);
        }
    }

    sort();

    return 0;
}

void calculate(char ch)
{
    ch = toupper(ch);
    if (isalpha(ch))
        arr[ch-'A']++;
}

void sort()
{
    int max, index;
    int i;
    for (; ;)
    {
        index = select();

        if (index == -1)
            return;

        max = arr[index];

        state[index] = true;

        for ( i = 0; i < N; i++)
        {
            if (!state[i] && arr[i] > max)
            {
                state[index] = false;
                state[i] = true;
                max = arr[i];
                index = i;
            }
        }

        printf("%c %d\n", index+'A', arr[index]);
    }
}

int select()
{
    int i;
    for ( i = 0; i < N; i++)
        if (!state[i] && arr[i])
            return i;
    return -1;
}