0x06. C - Pointers, arrays and strings.

Resources

Pointers, arrays and Data Structures
C - Arrays
C - Pointers
C - Strings
Memory Layout of C program

Tasks

All *-main.c files will be located in the test_files directory
We will be using function prototypes that will be included in our header file called, main.h.

0-main.c for testing

#include "main.h"
#include <stdio.h>

/**
 * main - check the code
 *
 * Return: Always 0.
 */
int main(void)
{
    char s1[98] = "Hello ";
    char s2[] = "World!\n";
    char *ptr;

    printf("%s\n", s1);
    printf("%s", s2);
    ptr = _strcat(s1, s2);
    printf("%s", s1);
    printf("%s", s2);
    printf("%s", ptr);
    return (0);
}

Expected ouput:

Hello 
World!
Hello World!
World!
Hello World!

compiled with:

gcc -Wall -pedantic -Werror -Wextra -std=gnu89 0-main.c 0-strcat.c -o 0-strcat

1. strncat

`[1-main.c](./test_files/1-main.c)` for testing

#include "main.h"
#include <stdio.h>

/**
 * main - check the code
 *
 * Return: Always 0.
 */
int main(void)
{
    char s1[98] = "Hello ";
    char s2[] = "World!\n";
    char *ptr;

    printf("%s\n", s1);
    printf("%s", s2);
    ptr = _strncat(s1, s2, 1);
    printf("%s\n", s1);
    printf("%s", s2);
    printf("%s\n", ptr);
    ptr = _strncat(s1, s2, 1024);
    printf("%s", s1);
    printf("%s", s2);
    printf("%s", ptr);
    return (0);
}

Compiled with:

gcc -Wall -pedantic -Werror -Wextra -std=gnu89 1-main.c 1-strncat.c -o 1-strncat

Expected ouput:

Hello 
World!
Hello W
World!
Hello W
Hello WWorld!
World!
Hello WWorld!

2. strncpy

main.c

#include "main.h"
#include <stdio.h>

/**
 * main - check the code
 *
 * Return: Always 0.
 */
int main(void)
{
    char s1[98];
    char *ptr;
    int i;

    for (i = 0; i < 98 - 1; i++)
    {
        s1[i] = '*';
    }
    s1[i] = '\0';
    printf("%s\n", s1);
    ptr = _strncpy(s1, "First, solve the problem. Then, write the code\n", 5);
    printf("%s\n", s1);
    printf("%s\n", ptr);
    ptr = _strncpy(s1, "First, solve the problem. Then, write the code\n", 90);
    printf("%s", s1);
    printf("%s", ptr);
    for (i = 0; i < 98; i++)
    {
        if (i % 10)
        {
            printf(" ");
        }
        if (!(i % 10) && i)
        {
            printf("\n");
        }
        printf("0x%02x", s1[i]);
    }
    printf("\n");
    return (0);
}

Compiled with

gcc -Wall -pedantic -Werror -Wextra -std=gnu89 2-main.c 2-strncpy.c -o 2-strncpy

Expected output

*************************************************************************************************
First********************************************************************************************
First********************************************************************************************
First, solve the problem. Then, write the code
First, solve the problem. Then, write the code
0x46 0x69 0x72 0x73 0x74 0x2c 0x20 0x73 0x6f 0x6c
0x76 0x65 0x20 0x74 0x68 0x65 0x20 0x70 0x72 0x6f
0x62 0x6c 0x65 0x6d 0x2e 0x20 0x54 0x68 0x65 0x6e
0x2c 0x20 0x77 0x72 0x69 0x74 0x65 0x20 0x74 0x68
0x65 0x20 0x63 0x6f 0x64 0x65 0x0a 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x2a 0x2a 0x2a 0x2a 0x2a 0x2a 0x2a 0x00

3. strcmp

main.c

#include "main.h"
#include <stdio.h>

/**
 * main - check the code
 *
 * Return: Always 0.
 */
int main(void)
{
    char s1[] = "Hello";
    char s2[] = "World!";

    printf("%d\n", _strcmp(s1, s2));
    printf("%d\n", _strcmp(s2, s1));
    printf("%d\n", _strcmp(s1, s1));
    return (0);
}

Compiled with:

gcc -Wall -pedantic -Werror -Wextra -std=gnu89 3-main.c 3-strcmp.c -o 3-strcmp

Expected output:

-15
15
0

4. I am a kind of paranoid in reverse. I suspect people of plotting to make me happy

main.c

#include "main.h"
#include <stdio.h>

/**
 * main - check the code
 * @a: an array of integers
 * @n: the number of elements to swap
 *
 * Return: nothing.
 */
void print_array(int *a, int n)
{
    int i;

    i = 0;
    while (i < n)
    {
        if (i != 0)
        {
            printf(", ");
        }
        printf("%d", a[i]);
        i++;
    }
    printf("\n");
}

/**
 * main - check the code
 *
 * Return: Always 0.
 */
int main(void)
{
    int a[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 98, 1024, 1337};

    print_array(a, sizeof(a) / sizeof(int));
    reverse_array(a, sizeof(a) / sizeof(int));
    print_array(a, sizeof(a) / sizeof(int));
    return (0);
}

Compiled with

gcc -Wall -pedantic -Werror -Wextra -std=gnu89 4-main.c 4-rev_array.c -o 4-rev_array

Expected output

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 98, 1024, 1337
1337, 1024, 98, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0

5. Always look up

main.c

#include "main.h"
#include <stdio.h>

/**
 * main - check the code
 *
 * Return: Always 0.
 */
int main(void)
{
    char str[] = "Look up!\n";
    char *ptr;

    ptr = string_toupper(str);
    printf("%s", ptr);
    printf("%s", str);
    return (0);
}

Compiled with

gcc -Wall -pedantic -Werror -Wextra -std=gnu89 5-main.c 5-string_toupper.c -o 5-string_toupper

Expected output

LOOK UP!
LOOK UP!

6. Expect the best. Prepare for the worst. Capitalize on what comes

main.c

#include "main.h"
#include <stdio.h>

/**
 * main - check the code
 *
 * Return: Always 0.
 */
int main(void)
{
    char str[] = "Expect the best. Prepare for the worst. Capitalize on what comes.\nhello world! hello-world 0123456hello world\thello world.hello world\n";
    char *ptr;

    ptr = cap_string(str);
    printf("%s", ptr);
    printf("%s", str);
    return (0);
}

Compiled with

gcc -Wall -pedantic -Werror -Wextra -std=gnu89 6-main.c 6-cap_string.c -o 6-cap

Expected output

Expect The Best. Prepare For The Worst. Capitalize On What Comes.
Hello World! Hello-World 0123456hello World Hello World.Hello World
Expect The Best. Prepare For The Worst. Capitalize On What Comes.
Hello World! Hello-World 0123456hello World Hello World.Hello World

7. Mozart composed his music not for the elite, but for everybody

main.c

#include "main.h"
#include <stdio.h>

/**
 * main - check the code for
 *
 * Return: Always 0.
 */
int main(void)
{
    char s[] = "Expect the best. Prepare for the worst. Capitalize on what comes.\n";
    char *p;

    p = leet(s);
    printf("%s", p);
    printf("%s", s);
    return (0);
}

Compiled with

gcc -Wall -pedantic -Werror -Wextra -std=gnu89 7-main.c 7-leet.c -o 7-1337

Expected output

3xp3c7 7h3 b3s7. Pr3p4r3 f0r 7h3 w0rs7. C4pi741iz3 0n wh47 c0m3s.
Expect the best. Prepare for the worst. Capitalize on what comes.

8. rot13

main.c

#include "main.h"
#include <stdio.h>

/**
 * main - check the code
 *
 * Return: Always 0.
 */
int main(void)
{
    char s[] = "ROT13 (\"rotate by 13 places\", sometimes hyphenated ROT-13) is a simple letter substitution cipher.\n";
    char *p;

    p = rot13(s);
    printf("%s", p);
    printf("------------------------------------\n");
    printf("%s", s);
    printf("------------------------------------\n");
    p = rot13(s);
    printf("%s", p);
    printf("------------------------------------\n");
    printf("%s", s);
    printf("------------------------------------\n");
    p = rot13(s);
    printf("%s", p);
    printf("------------------------------------\n");
    printf("%s", s);
    return (0);
}

Compiled with

gcc -Wall -pedantic -Werror -Wextra -std=gnu89 100-main.c 100-rot13.c -o 100-rot13

Expected output

EBG13 ("ebgngr ol 13 cynprf", fbzrgvzrf ulcurangrq EBG-13) vf n fvzcyr yrggre fhofgvghgvba pvcure.
------------------------------------
EBG13 ("ebgngr ol 13 cynprf", fbzrgvzrf ulcurangrq EBG-13) vf n fvzcyr yrggre fhofgvghgvba pvcure.
------------------------------------
ROT13 ("rotate by 13 places", sometimes hyphenated ROT-13) is a simple letter substitution cipher.
------------------------------------
ROT13 ("rotate by 13 places", sometimes hyphenated ROT-13) is a simple letter substitution cipher.
------------------------------------
EBG13 ("ebgngr ol 13 cynprf", fbzrgvzrf ulcurangrq EBG-13) vf n fvzcyr yrggre fhofgvghgvba pvcure.
------------------------------------
EBG13 ("ebgngr ol 13 cynprf", fbzrgvzrf ulcurangrq EBG-13) vf n fvzcyr yrggre fhofgvghgvba pvcure.

9. Numbers have life; they're not just symbols on paper

main.c

#include "main.h"

/**
 * main - check the code
 *
 * Return: Always 0.
 */
int main(void)
{
    print_number(98);
    _putchar('\n');
    print_number(402);
    _putchar('\n');
    print_number(1024);
    _putchar('\n');
    print_number(0);
    _putchar('\n');
    print_number(-98);
    _putchar('\n');
    return (0);
}

Compiled with

gcc -Wall -pedantic -Werror -Wextra -std=gnu89 _putchar.c 101-main.c 101-print_number.c -o 101-print_numbers

Expected output

10. A dream doesn't become reality through magic; it takes sweat, determination and hard work

main.c

#include <stdio.h>

int main(void)
{
  int n;
  int a[5];
  int *p;

  a[2] = 1024;
  p = &n;
  /*
   * write your line of code here...
   * Remember:
   * - you are not allowed to use a
   * - you are not allowed to modify p
   * - only one statement
   * - you are not allowed to code anything else than this line of code
   */
  ;
  /* ...so that this prints 98\n */
  printf("a[2] = %d\n", a[2]);
  return (0);
}

Compiled with

gcc -Wall -pedantic -Werror -Wextra -std=gnu89 102-main.c 102-magic.c -o 102-magic

Expected output

a[2] = 98

11. It is the addition of strangeness to beauty that constitutes the romantic character in art

main.c

#include "main.h"
#include <stdio.h>

/**
 * main - check the code
 *
 * Return: Always 0.
 */
int main(void)
{
        char *n = "1234567892434574367823574575678477685785645685876876774586734734563456453743756756784458";
        char *m = "9034790663470697234682914569346259634958693246597324659762347956349265983465962349569346";
        char r[100];
        char r2[10];
        char r3[11];
        char *res;

        res = infinite_add(n, m, r, 100);
        if (res == 0)
        {
                printf("Error\n");
        }
        else
        {
                printf("%s + %s = %s\n", n, m, res);
        }
        n = "1234567890";
        m = "1";
        res = infinite_add(n, m, r2, 10);
        if (res == 0)
        {
                printf("Error\n");
        }
        else
        {
                printf("%s + %s = %s\n", n, m, res);
        }
        n = "999999999";
        m = "1";
        res = infinite_add(n, m, r2, 10);
        if (res == 0)
        {
                printf("Error\n");
        }
        else
        {
                printf("%s + %s = %s\n", n, m, res);
        }
        res = infinite_add(n, m, r3, 11);
        if (res == 0)
        {
                printf("Error\n");
        }
        else
        {
                printf("%s + %s = %s\n", n, m, res);
        }
        return (0);
}

Compiled with

gcc -Wall -pedantic -Werror -Wextra -std=gnu89 103-main.c 103-infinite_add.c -o 103-add

Expected output

1234567892434574367823574575678477685785645685876876774586734734563456453743756756784458 + 9034790663470697234682914569346259634958693246597324659762347956349265983465962349569346 = 10269358555905271602506489145024737320744338932474201434349082690912722437209719106353804
Error
Error
999999999 + 1 = 1000000000

12. Noise is a buffer, more effective than cubicles or booth walls

main.c

#include "main.h"
#include <stdio.h>

/**
 * main - check the code
 *
 * Return: Always 0.
 */
int main(void)
{
    char buffer[] = "This is a string!\0And this is the rest of the #buffer :)\1\2\3\4\5\6\7#cisfun\n\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\x20\x21\x34\x56#pointersarefun #infernumisfun\n";

    printf("%s\n", buffer);
    printf("---------------------------------\n");
    print_buffer(buffer, sizeof(buffer));
    return (0);
}

Compiled with

gcc -Wall -pedantic -Werror -Wextra -std=gnu89 104-main.c 104-print_buffer.c -o 104-buffer

Expected output

This is a string!
---------------------------------
00000000: 5468 6973 2069 7320 6120 This is a 
0000000a: 7374 7269 6e67 2100 416e string!.An
00000014: 6420 7468 6973 2069 7320 d this is 
0000001e: 7468 6520 7265 7374 206f the rest o
00000028: 6620 7468 6520 2362 7566 f the #buf
00000032: 6665 7220 3a29 0102 0304 fer :)....
0000003c: 0506 0723 6369 7366 756e ...#cisfun
00000046: 0a00 0000 0000 0000 0000 ..........
00000050: 0000 0000 0000 0000 0000 ..........
0000005a: 2021 3456 2370 6f69 6e74  !4V#point
00000064: 6572 7361 7265 6675 6e20 ersarefun 
0000006e: 2369 6e66 6572 6e75 6d69 #infernumi
00000078: 7366 756e 0a00           sfun..

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0x06. C - Pointers, arrays and strings.

Resources

Tasks

[1-main.c](./test_files/1-main.c) for testing

Compiled with:

Expected ouput:

main.c

Compiled with

Expected output

main.c

Compiled with:

Expected output:

main.c

Compiled with

Expected output

main.c

Compiled with

Expected output

main.c

Compiled with

Expected output

main.c

Compiled with

Expected output

main.c

Compiled with

Expected output

main.c

Compiled with

Expected output

main.c

Compiled with

Expected output

main.c

Compiled with

Expected output

main.c

Compiled with

Expected output

`[1-main.c](./test_files/1-main.c)` for testing