project 3 by HIT

//
//  main.c
//  Assigend_3
//
//  Created by yarin ben baruch on 07/01/2020.
//  Copyright © 2020 yarin ben baruch. All rights reserved.
//

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

typedef char* verylong;
verylong input_long(void);
verylong add_verylong(verylong vl1, verylong vl2);
verylong multiply_verylong(verylong vl1, verylong vl2);


void main(void)
{
    verylong a, b, c;

    do {
        printf("enter the first long integer: ");
        a = input_long();
    } while (!a);

    do {

        printf("enter the second long integer: ");
        b = input_long();
    } while (!b);

    c = add_verylong(a, b);
    printf("%s + %s = %s\n", a, b, c);


    c = multiply_verylong(a, b); printf("%s * %s = %s\n", a, b, c);
    free(c);
    free(a);
    free(b);
}

verylong input_long(void)
{
    char tempstr[80];
    verylong longnum;
    int i = 0;

    longnum = (verylong)malloc((strlen(tempstr) + 1));

    gets(tempstr);

    while (tempstr[i] != '\0')
    {
        if (tempstr[i] < '0' || tempstr[i] > '9')
        {
            printf("Erorr,try again \n");
            return NULL;
        }
        i++;
    }

    strcpy(longnum, tempstr);

    return longnum;
}


verylong add_verylong(verylong vl1, verylong vl2)
{
    int i, carry = 0;
    int a, b, num;
    int size;
    int S_vl1 = strlen(vl1);
    int S_vl2 = strlen(vl2);
    int size_arr = (S_vl2 >= S_vl1 ? S_vl2 : S_vl1) + 1;

    verylong sum_arr = (verylong)calloc(size_arr + 1, sizeof(char));

    sum_arr[size_arr] = '\0';
    size = size_arr - 1;


    for (i = 0; i < size; i++)
    {
        a = vl1[S_vl1 - 1] - '0';
        b = vl2[S_vl2 - 1] - '0';

        if (S_vl1 - 1 < 0)
            a = 0;

        if (S_vl2 - 1 < 0)
            b = 0;

        num = a + b + carry;
        carry = num <= 9 ? 0 : 1;
        sum_arr[size_arr - 1] = (num <= 9 ? num : num % 10) + '0';

        size_arr--;
        S_vl1--;
        S_vl2--;
    }

    if (carry == 1)
        sum_arr[0] = '1';
    else
        sum_arr++;

    return sum_arr;

}


verylong multiply_verylong(verylong vl1, verylong vl2)
{
    int i = 0;
    int j = 0;
    int len1 = strlen(vl1);
    int len2 = strlen(vl2);
    int* result = (int*)calloc(len1 + len2, sizeof(int));
    int indexr1 = 0, indexr2 = 0;
    int carry;
    int n1;
    int n2;
    int sum;
    int z;
    for (i = len1 - 1; i >= 0; i--)
    {
        carry = 0;
        n1 = vl1[i] - '0';

        indexr2 = 0;

        for (j = len2 - 1; j >= 0; j--)
        {
            n2 = vl2[j] - '0';

            sum = n1 * n2 + result[indexr1 + indexr2] + carry;

            carry = sum / 10;

            result[indexr1 + indexr2] = sum % 10;

            indexr2++;
        }

        if (carry > 0)
            result[indexr1 + indexr2] += carry;
        indexr1++;
    }
    z = len1 + len2;

    while (z >= 0 && result[z - 1] == 0)
        z--;
    verylong longnum = (verylong)malloc(z + 1);
    if (z == 0) {
        longnum = (verylong)realloc(longnum, 2);
        longnum[0] = '0';
        longnum[1] = '\0';
        return longnum;
    }
    longnum[z] = '\0';
    z = z - 1;
    for (i = 0; z >= 0, longnum[i] != '\0'; i++, z--)
    {
        longnum[i] = result[z] + '0';
    }
    return longnum;
}