How to find and return a Maximum occurring Character in a Input String.

/***Write an efficient C function to return maximum occurring character in the input string e.g., if input string is “test string” then function should return ‘t’.
Input string = “test”
1: Construct character count array from the input string.
  count['e'] = 1
  count['s'] = 1
  count['t'] = 2

2: Return the index of maximum value in count array (returns ‘t’).
****/
#include <stdio.h>
#include <stdlib.h>
#define NO_OF_CHARS 256

int *getCharCountArray(char *);
char getIndexOfMax(int *, int);

/* Returns the maximum occurring character in
 the input string */
char getMaxOccuringChar(char *str)
{
  int *count = getCharCountArray(str);
  return getIndexOfMax(count, NO_OF_CHARS);
}

/* Returns an array of size 256 containg count
   of characters in the passed char array */
int *getCharCountArray(char *str)
{
  int *count = (int *)calloc(NO_OF_CHARS, sizeof(int));
  int i;

  for (i = 0; *(str+i);  i++)
    count[*(str+i)]++;

  return count;
}

char getIndexOfMax(int ar[], int ar_size)
{
  int i;
  int max_index = 0;

  for(i = 1; i < ar_size; i++)
    if(ar[i] > ar[max_index])
      max_index = i;

  /* free memory allocated to count */
  free(ar); 
  ar = NULL;

  return max_index;
}

int main()
{
  char str[] = "sample string";
  printf("%c", getMaxOccuringChar(str));

  getchar();
  return 0;
}

}

This post was written by: Naqushab Neyazee

CSE Undergraduate, AMU, Aligarh.

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Filed Under: c, character, count, efficient, program, string on Thursday, 29 May 2014