Question

How to sort a string with digits and letters (digits before letters) in C

Answer 1

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

int compare(const void *a, const void *b) {
    char charA = *(char *)a;
    char charB = *(char *)b;

    if (isdigit(charA) && isalpha(charB)) return -1; // Letters before digits
    if (isalpha(charA) && isdigit(charB)) return 1;  // Digits after letters
    return charA - charB;
}

int main() {
    char str[] = "d2c4b3a1";

    // Sort the characters using qsort and custom comparator
    qsort(str, strlen(str), sizeof(char), compare);

    printf("%s\n", str);
    
    return 0;
}


/*
run:

1234abcd

*/

 

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