Digit Frequency calculating code in C not working-CodePudding

So, I was writing this code for counting the digit frequency i.e. the number of times the digits from 0-9 has appeared in a user inputted string(alphanumeric). So, I took the string, converted into integer and tried to store the frequency in "count" and print it but when I run the code, count is never getting incremented and the output comes all 0s. Would be grateful if anyone points out in which part my logic went wrong.

#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>

int main() {
    // takes string input
    char *s;
    s = malloc(1024 * sizeof(char));
    scanf("%[^\n]", s);
    s = realloc(s, strlen(s)   1);
    //turns the string to int
    int x = atoi(s);
    int temp = x, len = 0;
    //calculates string length
    while (x != 0) {
        x = x / 10;
        len  ;
    }
    x = temp;
    //parses through the string and matches digits with each number
    for (int j = 0; j < 10; j  ){
        int count = 0;
        for(int i = 0; i < len; i  ){
            if(x % 10 == j){
                count  ;
            }
            x = x / 10;
        }
        x = temp;
        printf("%d ", count);
    }
    return 0;
}

CodePudding user response：

To write a correct and reasonable digit-counting program:

Do not allocate any buffer for this.
Create an array to count the number of times each digit occurs. The array should have ten elements, one for each digit.
Initialize the array to zero in each element.
In a loop, read one character at a time.
Leave the loop when the read routine (such as getchar) indicates end-of-file or a problem, or, if desired, returns a new-line or other character you wish to use as an end-of-input indication.
Inside the loop, check whether the character read is a digit. If the character read is a digit, increment the corresponding element of the array.
After the loop, execute a new loop to iterate through the digits.
Inside that loop, for each digit, print the count from the array element for that digit.

CodePudding user response：

Your approach is way to complicated for a very easy task. This will do:

void numberOfDigits(const char *s, int hist[10]) {
    while(*s) {
        if(isdigit(*s)) 
            hist[*s - '0']  ;
        s  ;
    }
}

It can be used like this:

int main(void) {
    char buf[1024];
    int hist[10];

    fgets(buf, sizeof buf, stdin);

    numberOfDigits(s, hist);

    for(int i=0; i<10; i  ) 
        printf("Digit %d occurs %d times\n", i, hist[i]);
}

This can also be quite easily achieved without a buffer if desired:

int ch;
int hist[10];

while((ch = getchar()) != EOF) {
    if(isdigit(ch)) 
        hist[ch - '0']  ;
}