Easy - Divisible Sum Pairs.c

#include <assert.h>
#include <ctype.h>
#include <limits.h>
#include <math.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char* readline();
char* ltrim(char*);
char* rtrim(char*);
char** split_string(char*);

int parse_int(char*);

/*
 * Complete the 'divisibleSumPairs' function below.
 *
 * The function is expected to return an INTEGER.
 * The function accepts following parameters:
 *  1. INTEGER n
 *  2. INTEGER k
 *  3. INTEGER_ARRAY ar
 */

int divisibleSumPairs(int n, int k, int ar_count, int* ar)
{
    int divisible_pairs = 0;
    
    for(int i = 0 ; i < ar_count-1 ; i++)
    {
        for(int j = i+1 ; j < ar_count ; j++)
        {
            if(((ar[i] + ar[j]) % k) == 0)
                divisible_pairs++;
        }
    }
    return divisible_pairs;
}

int main()
{
    FILE* fptr = fopen(getenv("OUTPUT_PATH"), "w");

    char** first_multiple_input = split_string(rtrim(readline()));

    int n = parse_int(*(first_multiple_input + 0));

    int k = parse_int(*(first_multiple_input + 1));

    char** ar_temp = split_string(rtrim(readline()));

    int* ar = malloc(n * sizeof(int));

    for (int i = 0; i < n; i++)
    {
        int ar_item = parse_int(*(ar_temp + i));

        *(ar + i) = ar_item;
    }

    int result = divisibleSumPairs(n, k, n, ar);

    fprintf(fptr, "%d\n", result);

    fclose(fptr);

    return 0;
}

char* readline()
{
    size_t alloc_length = 1024;
    size_t data_length = 0;

    char* data = malloc(alloc_length);

    while (true)
    {
        char* cursor = data + data_length;
        char* line = fgets(cursor, alloc_length - data_length, stdin);

        if (!line)
        {
            break;
        }

        data_length += strlen(cursor);

        if (data_length < alloc_length - 1 || data[data_length - 1] == '\n')
        {
            break;
        }

        alloc_length <<= 1;

        data = realloc(data, alloc_length);

        if (!data)
        {
            data = '\0';

            break;
        }
    }

    if (data[data_length - 1] == '\n')
    {
        data[data_length - 1] = '\0';

        data = realloc(data, data_length);

        if (!data)
        {
            data = '\0';
        }
    }
    else
    {
        data = realloc(data, data_length + 1);

        if (!data)
        {
            data = '\0';
        }
        else
        {
            data[data_length] = '\0';
        }
    }

    return data;
}

char* ltrim(char* str)
{
    if (!str)
    {
        return '\0';
    }

    if (!*str)
    {
        return str;
    }

    while (*str != '\0' && isspace(*str))
    {
        str++;
    }

    return str;
}

char* rtrim(char* str)
{
    if (!str)
    {
        return '\0';
    }

    if (!*str)
    {
        return str;
    }

    char* end = str + strlen(str) - 1;

    while (end >= str && isspace(*end))
    {
        end--;
    }

    *(end + 1) = '\0';

    return str;
}

char** split_string(char* str)
{
    char** splits = NULL;
    char* token = strtok(str, " ");

    int spaces = 0;

    while (token)
    {
        splits = realloc(splits, sizeof(char*) * ++spaces);

        if (!splits)
        {
            return splits;
        }

        splits[spaces - 1] = token;

        token = strtok(NULL, " ");
    }

    return splits;
}

int parse_int(char* str)
{
    char* endptr;
    int value = strtol(str, &endptr, 10);

    if (endptr == str || *endptr != '\0')
    {
        exit(EXIT_FAILURE);
    }

    return value;
}