Sock Merchant

[Algorithms > Implementation]

https://www.hackerrank.com/challenges/sock-merchant/problem 

배열의 크기(n)을 입력하고,

배열의 원소들을 입력한다.

배열들 중 같은 숫자들의 쌍의 개수 (2개씩)를 출력하는 문제

#include <assert.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** split_string(char*);

// Complete the sockMerchant function below.
int sockMerchant(int n, int ar_count, int* ar) {
    int pair=0;
    int a[n];
    int p[n];
    a[0]=ar[0];
    p[0]=1;
    int ind=0, j;
    for(int i=1;i<n;i++){
        for(j=0;j<=ind;j++){
            if(ar[i]==a[j]) {p[j]++;    break;}
        }
        if(j>ind){
            ind++;
            a[ind]=ar[i];
            p[ind]=1;
        }
    }
    for(int i=0;i<=ind;i++){
        pair += (p[i]/2);
    }
    return pair;
}

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

    char* n_endptr;
    char* n_str = readline();
    int n = strtol(n_str, &n_endptr, 10);

    if (n_endptr == n_str || *n_endptr != '\0') { exit(EXIT_FAILURE); }

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

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

    for (int i = 0; i < n; i++) {
        char* ar_item_endptr;
        char* ar_item_str = *(ar_temp + i);
        int ar_item = strtol(ar_item_str, &ar_item_endptr, 10);

        if (ar_item_endptr == ar_item_str || *ar_item_endptr != '\0') { exit(EXIT_FAILURE); }

        *(ar + i) = ar_item;
    }

    int ar_count = n;

    int result = sockMerchant(n, ar_count, 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; }

        size_t new_length = alloc_length << 1;
        data = realloc(data, new_length);

        if (!data) { break; }

        alloc_length = new_length;
    }

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

    data = realloc(data, data_length);

    return data;
}

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;
}