Maximum number of Characters in a character array

Question

//Program to find max occurring character in string

#include<stdio.h>
#include<conio.h>
#define MAX_SIZE 100  // Maximum string size, change to make string smaller or larger
#define MAX_CHARS 255 // Maximum characters allowed for characters


void main()
{
    char str[MAX_SIZE];  //store the string
    int freq[MAX_CHARS]; // store frequency of each character
    int i, max; // i is for loop max to store frequency
    int ascii;   //stores ascii value convertd from each char
    char ch;    //for choice

    do{
        clrscr();
        i=0;
    printf("\nEnter any string: ");
    gets(str);

    // Initializes frequency of all characters to 0
    for(i=0; i<MAX_CHARS; i++)
    {
    freq[i] = 0;
    }


    // Finds occurance/frequency of each characters
    i=0;
    while(str[i] != '\0')
    {
    ascii = (int)str[i];
    freq[ascii] += 1;       //string's element is casted to int to store its ascii value for further comparision

    i++;
    }


    // Finds maximum frequency of character
    max = 0;
    for(i=0; i<MAX_CHARS; i++)
    {
    if(freq[i] > freq[max])
        max = i;            //to print no. of times 
    }


    printf("\nMaximum occurring character is '%c' = %d times.", max, freq[max]);
    printf("\n Want to find again??(y/n):");
    scanf("%c",&ch);
    }while(ch=='Y'||ch=='y');
}

When I give it the input: "aaaaeeee", the output is "a" occurring 4 times, but "e" occurs 4 times too. I know this is sorted by ascii values and thats why it gives "a" as output, but what can I do in this program that the output gives both "a" and "e" as output when a case like this occurs?

side note: Don't use void main(), use int main()..And `conio.h` header as well. — danglingpointer, Nov 21 '17 at 09:02
Please go through this question, where the return type of main is discussed in detail: https://stackoverflow.com/questions/204476/what-should-main-return-in-c-and-c — danglingpointer, Nov 21 '17 at 09:05
And never, never, never use `gets`, use `fgets` (or POSIX `getline`) `gets` is so insecure and so vulnerable to buffer overrun, it has been removed from the C11 library. Toss it. If your prof wants you to use it, toss him too. — David C. Rankin, Nov 21 '17 at 09:05
this isnt college work or anything, its for my own curiosity to learn coding, and i will take care of it. — Fluffy Bunny, Nov 21 '17 at 09:16

Déjà vu · Accepted Answer · 2017-11-21T09:35:02.817

Add max calculation ahead

 i = 0;
 max = 0;
 while(str[i] != '\0')
 {
    ascii = (int)str[i];
    freq[ascii] += 1;
    if (freq[ascii] > max) max = freq[ascii]; // <==== here
    i++;
 }

Note that this is the max number of the same character you might have.

Then display all chars which maximum is equal to max

for(i=0; i<MAX_CHARS; i++)
{ 
   if(freq[i] == max) printf("Character %c is at max %d\n", i, max);
}

To fix the endless loop, before the while add char c ; while ((c = getchar()) != EOF && c != '\n');

   scanf("%c",&ch);
   char c;
   while ((c = getchar()) != EOF && c != '\n'); // <== note the ';'
} while(ch=='Y'||ch=='y');

Note that you shouldn't use gets, reason is explained here.

Whole code:

void main()
{
    char str[MAX_SIZE];  //store the string
    int freq[MAX_CHARS]; // store frequency of each character
    int i, max; // i is for loop max to store frequency
    int ascii;   //stores ascii value convertd from each char
    char ch;    //for choice

    do {
        printf("\nEnter any string: ");
        gets(str);

        // Initializes frequency of all characters to 0
        for(i=0; i<MAX_CHARS; i++)
        {
            freq[i] = 0;
        }


        // Finds occurance/frequency of each characters
        for(i=0,max=0 ; str[i] != '\0' ; i++)
        {
            ascii = (int)str[i];
            freq[ascii] += 1;       //string's element is casted to int to store its ascii value for further comparision
            if (freq[ascii] > max) max = freq[ascii];
        }

        for(i=0; i<MAX_CHARS; i++)
        { 
            if(freq[i] == max) printf("Character %c is at max %d\n", i, max);
        }

        printf("\n Want to find again??(y/n):");
        scanf("%c",&ch);
        char c;
        while ((c = getchar()) != EOF && c != '\n'); 
    }while(ch=='Y'||ch=='y');
}

theres just one problem, when i re-run the code by typing 'y' when prompted if i wanna find again or not, at that time the output shows every character in ASCII, and does not take input — Fluffy Bunny, Nov 21 '17 at 09:12
See https://stackoverflow.com/questions/24073138/good-way-to-flush-scanf-buffer-when-invalid-entry-entered . Basically add `char c ; while ((c = getchar()) != EOF && c != '\n'); ` before the ending `while`. — Déjà vu, Nov 21 '17 at 09:14
the output is wrong after code is re-run, even without re-run, its wrong in somecases like "aaaa" output is "Character a is at max 2" — Fluffy Bunny, Nov 21 '17 at 09:30
Of course the `i++` had to be removed in the 'whole code' - I changed the `i=0 ; while ...` to `for ...` thus `i` was incremented twice. Code edited! — Déjà vu, Nov 21 '17 at 09:34

score 1 · Answer 2 · answered Nov 21 '17 at 09:05

Above this line

printf("\nMaximum occurring character is '%c' = %d times.", max, freq[max]);

Delete it and add this code

for(i=0;i<MAX_CHARS;i++)
{
    if(freq[i]==freq[max])
    {
        printf("\nMaximum occurring character is '%c' = %d times.", i, freq[i]);
    }
}

Maximum number of Characters in a character array

2 Answers2