c concat

// eh.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <random>
#include <time.h>

int _tmain(int argc, _TCHAR* argv[])
{
    clock_t begin, end;
    clock_t petla_begin, petla_end;

    double time_spent = 0;
    double total_time = 0;
    //total_time += time_spent;

    bool a = true;
    int len_a = 0;
    int len_b = 0;
    int n = 0;

    char str_a[1000];
    char str_b[1000];

    char* str_c;

    int ch, lastch = '\0';
    begin = clock();
    while ((ch = getchar()) != EOF)
    {
        if (ch == 10)
        {
            a = !a;

            str_c = (char *)malloc(sizeof(char) * (len_a + len_b + 3));
            //strcat(str_c, str_a);
            strncpy(str_c, str_a, len_a);
            //strcat(str_c, str_b);
            strncpy(str_c + len_a, str_b, len_b);

            //str_c[len_a + len_b] = '\0';

            n++;

            free(str_c);
            len_a = 0;
            len_b = 0;
        }
        else if (ch == 32)
        {
            a = !a;
        }
        else
        {
            if (a)
            {
                str_a[len_a] = ch;
                len_a++;
            }
            else
            {
                str_b[len_b] = ch;
                len_b++;
            }
        }

    }

    end = clock();

    petla_begin = clock();
    long ij = 0;
    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < 1000; j++)
        {
            ij++;
        }
    }
    petla_end = clock();
    time_spent = (double)(end - begin) - (double)(petla_end-petla_begin);
    time_spent = time_spent /  CLOCKS_PER_SEC;
    printf("total time: %.50f\n", time_spent);
    printf("avg: %.50f\n", time_spent / n);

    return (int)ij;
}