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

void myFgets(char str[], int len);
void lettersInStr(char str[], int lett[], int strSize);
void checkMax(int letter[], int letterSize);
void exchangeLetters(char str[], int strSize);

char maxCh='a';
char secMaxCh='a';

int main (void)
{
	char string[100]={0};
	int letters[26]={0};

	printf("Enter a string:\n");
	myFgets(string, 100);

	lettersInStr(string, letters, strlen(string));
	checkMax(letters, AMOUNT_OF_LETTERS);

	exchangeLetters(string, strlen(string));

	printf("Most common: %c, 2nd most common: %c\n", maxCh, secMaxCh);
	printf("Swapped:\n");
	printf("%s", string);
    return 0;
}

//a function that removes the enter
void myFgets(char str[], int len)
{
	fgets(str, len, stdin);
	str[strcspn(str, "\n")]=0;
}

// a function that check how many times every latter was in the string
void lettersInStr(char str[], int letter[], int strSize)
{
	int i=0;

	for(i=0; i<strSize; i++)
	{
		letter[str[i]-'a']++;
	}

}
// a function that checks what is the latter that appeared the most times
void checkMax(int letter[], int letterSize)
{
	int i=0;
	int j=0;
	int tmp=0;

	int max=0;
	int secMax=0;

	max=-1;
	secMax=-1;
	for(i=0; i<letterSize; i++)
	{
		if(letter[i]>max) /
		{
			max=letter[i];
			maxCh=i+'a';
			tmp=i;
		}
	}


	for(j=0; j<letterSize; j++)
	{
		if(letter[j]>secMax && letter[j]<=max && j!=tmp)

		{
			secMax=lett[j];
			secMaxCh=j+'a';
		}
	}
}


void exchangeLetters(char str[], int strSize)
{
	int i=0;

	for(i=0; i<strSize; i++)
	{
		if(str[i]==maxCh)
		{
			str[i]=secMaxCh;
		}
		else if(str[i]==secMaxCh)
		{
			str[i]=maxCh;
		}
	}
}