counting sort

#include <stdio.h> 
#include <string.h> 
#define RANGE 255 
  

void countSort(char arr[]) 
{ 
   
    char output[strlen(arr)]; 
  
    
    int count[RANGE + 1], i; 
    memset(count, 0, sizeof(count)); 
  
    
    for(i = 0; arr[i]; ++i) 
        ++count[arr[i]]; 
  
   
    
    for (i = 1; i <= RANGE; ++i) 
        count[i] += count[i-1]; 
  
    
    for (i = 0; arr[i]; ++i) 
    { 
        output[count[arr[i]]-1] = arr[i]; 
        --count[arr[i]]; 
    } 
  
    /* 
     For Stable algorithm  
     for (i = sizeof(arr)-1; i>=0; --i) 
    { 
        output[count[arr[i]]-1] = arr[i]; 
        --count[arr[i]]; 
    } 
     
    For Logic : See implementation 
    */
  
    for (i = 0; arr[i]; ++i) 
        arr[i] = output[i]; 
} 
  

int main() 
{ 
    char arr[];
	printf("enter the string");
	scanf("%S",arr);
  
    countSort(arr); 
  
    printf("Sorted character array is %sn", arr); 
    return 0; 
}