How to identify specific digits of an integer input in C?

#include "stdio.h"

int main(){
    int digits[] = {0,0,0,0,0,0,0,0,0,0};
    int i = 11031;

    while(i > 0){
    	digits[i % 10]++;
    	i = i / 10;
    }

    printf("There are %d ones.n", digits[1]);
}

int val; //Input
 ...
 int ones = 0;
 while(val != 0) {
   ones += ((val % 10) == 1) ? 1 : 0;
   val /= 10;
 }

while(*str != '') {
  if(*str++ == '1') {
    ones++;
  }
}

"java".charAt(i) == "c the language"[i];

int val=11031;
int count=0;
int i=0;
char buf[100];
sprint(buf, "%d", val);
for(i=0; (i < sizeof(buf)) && (buf[i]); i++) {
  if(buf[i] == '1')
    count++;
}

int digit = 0;
int value = 11031;

while(value > 0)
{
    digit = value % 10;
    /* Do something with digit... */
    value = value / 10;
}

int count_digit(int nr, int digit) {
    int count=0;
    while(nr>0) {
      if(nr%10==digit)
        count++;
      nr=nr/10;
    }
    return count;
}

int count_digits(int digit, const char *in)
{
   int ii, count = 0;
   if (digit < 0 || digit > 9) return -0;
   digit = digit + (int)'0'; /* make the digit the correct ascii value */

   for (ii = 0; in[ii] != ''; ++ii)
   {
      if (in[ii] == (char)digit) count++;
   }

   return count;
}

int count_chars(char ch, const char *in)
{
   int ii, count = 0;
   for (ii = 0; in != NULL && in[ii] != ''; ++ii)
   {
      if (in[ii] == ch) count++;
   }

   return count;
}

int countOnes(int input)
{
    int result = 0;
    while(input) {
        result += ((input%10)==1);
        result /= 10;
    }
    return result;
}

int countOnes(char *input)
{
    int result = 0;
    while(input && *input) {
        result += (*input++ == '1');
    }
    return result;
}

int countDigit(int Number, int Digit)
{
   int counter = 0;

   do
   {
      if( (Number%10) == Digit)
      {
         counter++;
      }
   }while(Digit>0)

   return counter;
}

#include <stdio.h>

main() {
        char buf[100];
        char *p = buf;
        int n = 0;
        scanf("%s", buf);
        while (*p) {
                if (*p == '1') {
                        n++;
                }
                p++;
        }
        printf ("'%s' contains %i onesn", buf, n);
}

int count_digits(int n, int d) {
  int count = 0;
  while(n*10/=10) if (n%10==d) count++
  return count;
}