Question

Part 1 Write a program that reads a line of input and display the characters between the first two '*' characters. If no two '*' occur, the program should display a message about not finding two * characters.

For example, if the user enters: 1abc*D2Efg_#!*345Higkl*mn+op*qr the program should display the following: D2Efg_#!

1) Name your program stars.c.

2) Assume input is no more than 1000 characters.

3) String library functions are NOT allowed in this program.

4) To read a line of text, use the read_line function (the pointer version) in the lecture notes.

5) Include and call the search function. The search function expects s1 to point to a string containing the input as a string and stores the characters between the first two '*' to the string pointed by s2. If the input does not contain two '*', s2 should contain an empty string. An empty string is a valid string with no characters except the null character. The function returns 1 if the input contains two '*', and returns 0 otherwise.

int search (char *s1, char *s2);

6) The search function should use pointer arithmetic (instead of array subscripting). In other words, eliminate the loop index variables and all use of the [] operator in the function.

7) The main function should display the output

comments and steps would be helpful Thanks

Part 2 is to modify part 1 of the program so that input comes in as command line arguments.

Sample run: ./a.out W8 4 ME 2 finish 2!

Output: Consonants: WMfnsh

Answer 1

"stars.c" code screenshot:

"stars.c" code:

#include <stdio.h>

// this function is already given
int read_line(char *str, int n)
{
    int ch, i = 0;
    while ((ch = getchar()) != '\n')
    {
        if (i < n)
        {
            *str++ = ch;
            i++;
        }
    }
    *str = '\0';
    return i;
}

int search(char *s1, char *s2)
{
    // First we have to find if the input string contains
    // atleast two '*'. If not found then return 0.
    int cntStar = 0;
    // when we will find two '*' then break the loop
    while (*s1 != '\0' && cntStar < 2)
    {
        if (*s1++ == '*')
            cntStar++;
    }
    // if atleast two '*' not found then return 0 with
    // empty string with null
    if (cntStar < 2)
    {
        *s2 = '\0';
        return 0;
    }
    else
    {
        // Here we will find the characters between the first two '*'

        // Currently s1 is not pointing first '*' character
        // So, we need to move back using decrement operator
        while (cntStar > 0)
        {
            s1--;
            if (*s1 == '*')
                cntStar--;
        }

        int isFirstStar = 0;
        while (*s1 != '\0')
        {
            // if below condition is met, then character is our first '*'
            if (*s1 == '*' && isFirstStar == 0)
            {
                isFirstStar = 1;
            }
            // if below condition is met, then character is our second '*'
            // and hence we will return to main() function
            else if (*s1 == '*' && isFirstStar == 1)
            {
                *s2 = '\0';
                return 1;
            }
            // if we encountered first '*' character previously
            // then keep storing the characters in s2
            else if (isFirstStar == 1)
            {
                *s2++ = *s1;
            }
            // increment to get next character
            s1++;
        }
        return 1;
    }
}

int main()
{
    char str1[1000];
    char str2[1000];
    int size, isValid;

    printf("Enter input string: ");
    size = read_line(str1, 1000);
    isValid = search(str1, str2);

    if (isValid == 0)
        printf("\nUnable to find two '*' !!!");
    else
        printf("\nOutput: %s", str2);
    return 0;
}

Output: