#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define SIZE 300
#define FLUSH stdin=freopen(NULL, "r", stdin)
#define RMN(str) str[strcspn(str,"\n")] = 0

void frequencyAnalysis(char[], char);
void search(char*, char*);
void decrypt(char, char[]);

int main(int argc, char** argv) {
    char str[SIZE];
    char res[SIZE];
    char flag;
    do{
        flag = 0;

        printf("Input number string with length of %d ", SIZE);
        fgets(str, sizeof(str), stdin);
        FLUSH;
        RMN(str);

        if(strlen(str) < 1 || strlen(str) > SIZE){
            printf("please try again");
            flag = 1;
        }
    }while (flag);

    search(str, res);
    FLUSH;
    printf("most frequent char is %s", res);

    return 0;
}

void search(char *string, char* threeMostCommonChars){
    int count[SIZE] = {0}, i;
    for(i = 0; string[i]; i++){
        if(string[i] != ' '){
        (count[string[i]])++;
        }
    }

    int first = 0, second = 0, third =0;

    for(i = 0; i < SIZE; i++){
        if(count[i] > count[first]){
            third = second;
            second = first;
            first = i;
        }
        else if(count[i] > count[second] &&
                 count[i] != count[first]){
            third = second;
            second = i;
        }
        else if(count[i] > count[third] &&
                count[i] != count[second]){
            third = i;
            FLUSH;
        }
    }
    char mostCommonChars[3] = {first, second, third};
    FLUSH;
    strcpy(threeMostCommonChars, mostCommonChars);
}


void frequencyAnalysis(char string[], char mostFrequentChar){
    char shift = 'e' - mostFrequentChar;
    decrypt(shift, string);
    printf("\nchanging %c->%c(shift %d) %s", mostFrequentChar, 'e', shift, string);
}


void decrypt(char shift, char string[]){
    //reference problem2_initial.txt
    size_t i = 0;
    while(string[i]){
        if(string[i] >= 'a' && string[i]<= 'z'){
            string[i] = (string[i] + shift - 'a')%26 + 'a';
        }
        if(string[i] >= 'A' && string[i]<='Z'){
            string[i] = (string[i] + shift - 'A')%26 + 'A';
        }
        i++;
    }
}