50206. Three Letter Pattern

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include <string.h>

typedef struct{
    int num;
    int cnt;
} s_info;

int n;
char s[100005];
s_info info[17576];

int cmp(const void* aa, const void* bb){
    s_info* a = (s_info*)aa;
    s_info* b = (s_info*)bb;
    if(a->cnt != b->cnt) return b->cnt - a->cnt;
    return a->num - b->num;
}

int mapping(int i){
    return ((s[i] - 'a') * (26 * 26) + (s[i + 1] - 'a') * (26) + (s[i + 2] - 'a'));
}
void to_str(int k){
    int s1 = k / (26 * 26); k %= (26 * 26);
    int s2 = k / 26; k %= 26;
    int s3 = k;
    printf("%c%c%c\n", s1 + 'a', s2 + 'a', s3 + 'a');
}


int main(){
    fgets(s, 100005, stdin);
    n = strlen(s);

    for(int i = 0; i < 17576; i++) info[i].num = i, info[i].cnt = 0;

    for(int i = 0; i < n - 3; i++){
        if(s[i] == ' ' || s[i + 1] == ' ' || s[i + 2] == ' ') continue;
        int num = mapping(i);
        info[num].cnt += 1;
    }
    qsort(info, 17576, sizeof(s_info), cmp);
    for(int i = 0; i < 3; i++){
        to_str(info[i].num);
    }
}