Find Maximum Occurrence of Character in a String in C

An array of characters is called a string.

Declaration

Following is the declaration declaring an array is as follows ?

char stringname [size];

For example: char string[50]; string of length 50 characters

Initialization

• Using single character constant ?

char string[10] = { ?H', ?e', ?l', ?l', ?o' ,?\0'}

• Using string constants ?

char string[10] = "Hello":;

Accessing ? There is a control string "%s" used for accessing the string till it encounters ?\0'.

Finding maximum occurrence

The logic to find the maximum occurrence of character is ?

• First, find frequency of characters, by using the following program.

while(string[i] != '\0'){
  value = (int)string[i];
  frequency[value] += 1;
  i++;
}

• Based on this, we are finding maximum occurrence character.

maximum = 0;
for(i=0; i<CHARS; i++){
  if(frequency[i] > frequency[maximum])
    maximum = i;
}

Example

Given below is the C program to find max occurring character in a string ?

#include <stdio.h>

#define SIZE 100 // Maximum string size
#define CHARS 255 // Maximum characters allowed

int main() {
  char string[SIZE];
  int frequency[CHARS];
  int i = 0, maximum;
  int value;
  
  printf("Enter the string:
 ");
  gets(string);
  
  for (i = 0; i < CHARS; i++) {
    frequency[i] = 0; // initialize freq of all characters to zero
  }
  
  /* Finds frequency of each characters */
  i = 0;
  while (string[i] != '\0') {
    value = (int) string[i];
    frequency[value] += 1;
    i++;
  }
  
  /* Finds maximum frequency */
  maximum = 0;
  for (i = 0; i < CHARS; i++) {
    if (frequency[i] > frequency[maximum])
      maximum = i;
  }
  
  printf("Maximum occurrence character is '%c' = %d times.", maximum,
    frequency[maximum]);
  return 0;
}

Output

When the above program is executed, it produces the following result ?

Enter the string:
tutorials point
Maximum occurrence character is 't' = 3 times.