Question

How to sort an array of strings where each string represents a decimal number in C

Answer 1

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

// Comparator function to sort strings as decimal numbers
int compareAsDecimal(const void* a, const void* b) {
    // Convert strings to double for comparison
    const char* strA = *(const char**)a;
    const char* strB = *(const char**)b;

    double numA = strtod(strA, NULL);
    double numB = strtod(strB, NULL);

    if (numA < numB) return -1;
    if (numA > numB) return 1;
    
    return 0;
}

int main() {
    // Input array of strings
    const char* numbers[] = {"12.3", "5.6", "789.1", "3.14", "456.0", "0", "0.01", "4.0"};
    int size = sizeof(numbers) / sizeof(numbers[0]);

    // Sort the array using the custom comparator
    qsort(numbers, size, sizeof(char*), compareAsDecimal);

    // Print the sorted array
    printf("Sorted array of decimal strings:\n");
    for (int i = 0; i < size; ++i) {
        printf("%s  ", numbers[i]);
    }

    return 0;
}



/*
run:

Sorted array of decimal strings:
0  0.01  3.14  4.0  5.6  12.3  456.0  789.1  

*/

 

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