0x06-pointers_arrays_strings

More pointers, arrays and strings

• What are pointers and how to use them
• What are arrays and how to use them
• What are the differences between pointers and arrays
• How to use strings and how to manipulate them
• Scope of variables

0. strcat

Write a function that concatenates two strings.

• Prototype: char *_strcat(char *dest, char *src);
• This function appends the src string to the dest string, overwriting the terminating null byte (\0) at the end of dest, and then adds a terminating null byte
• Returns a pointer to the resulting string dest

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1. strncat

Write a function that concatenates two strings.

• Prototype: char *_strncat(char *dest, char *src, int n);
• The _strncat function is similar to the _strcat function, except that
  • it will use at most n bytes from src; and
  • src does not need to be null-terminated if it contains n or more bytes
• Return a pointer to the resulting string dest

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2. strncpy

Write a function that copies a string.

• Prototype: char *_strncpy(char *dest, char *src, int n);

• Your function should work exactly like strncpy

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3. strcmp

Write a function that compares two strings.

• Prototype: int _strcmp(char *s1, char *s2);
• Your function should work exactly like strcmp

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

Write a function that reverses the content of an array of integers.

• Prototype: void reverse_array(int *a, int n);
• Where n is the number of elements of the array

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5. Always look up

Write a function that changes all lowercase letters of a string to uppercase.

• Prototype: char *string_toupper(char *);

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

Write a function that capitalizes all words of a string.

• Prototype: char *cap_string(char *);
• Separators of words: space, tabulation, new line, ,, ;, ., !, ?, ", (, ), {, and }

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

Write a function that encodes a string into 1337.

• Letters a and A should be replaced by 4

• Letters e and E should be replaced by 3

• Letters o and O should be replaced by 0

• Letters t and T should be replaced by 7

• Letters l and L should be replaced by 1

• Prototype: char *leet(char *);

• You can only use one if in your code

• You can only use two loops in your code

• You are not allowed to use switch

• You are not allowed to use any ternary operation

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8. rot13

Write a function that encodes a string using rot13.

• Prototype: char *rot13(char *);

• You can only use if statement once in your code

• You can only use two loops in your code

• You are not allowed to use switch

• You are not allowed to use any ternary operation

solution

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

Write a function that prints an integer.

• Prototype: void print_number(int n);
• You can only use _putchar function to print
• You are not allowed to use long
• You are not allowed to use arrays or pointers
• You are not allowed to hard-code special values

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

Add one line to this code, so that the program prints a[2] = 98, followed by a new line.

• You are not allowed to use the variable a in your new line of code
• You are not allowed to modify the variable p
• You can only write one statement
• You are not allowed to use ,
• You are not allowed to code anything else than the line of expected line of code at the expected line
• Your code should be written at line 19, before the ;
• Do not remove anything from the initial code (not even the comments)
• and don’t change anything but the line of code you are adding (don’t change the spaces to tabs!)
• You are allowed to use the standard library

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

Write a function that adds two numbers.

• Prototype: char *infinite_add(char *n1, char *n2, char *r, int size_r);

• Where n1 and n2 are the two numbers

• r is the buffer that the function will use to store the result

• size_r is the buffer size

• The function returns a pointer to the result

• You can assume that you will always get positive numbers, or 0

• You can assume that there will be only digits in the strings n1 and n2

• n1 and n2 will never be empty

• If the result can not be stored in r the function must return 0

solution

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

Write a function that prints a buffer.

• Prototype: void print_buffer(char *b, int size);

• The function must print the content of size bytes of the buffer pointed by b

• The output should print 10 bytes per line

• Each line starts with the position of the first byte of the line in hexadecimal (8 chars), starting with 0

• Each line shows the hexadecimal content (2 chars) of the buffer, 2 bytes at a time, separated by a space

• Each line shows the content of the buffer. If the byte is a printable character, print the letter, if not, print .

• Each line ends with a new line \n

• If size is 0 or less, the output should be a new line only \n

• You are allowed to use the standard library

solution