Question

please write the code in C not c++, and not to use Atoi or parseint to parse the string, Thank you.

#include <stdio.h>

#include <stdbool.h>

/*

* The isinteger() function examines the string given as its first

* argument, and returns true if and only if the string represents a

* well-formed integer. A well-formed integer consists only of an

* optional leading - followed by one or more decimal digits.

* Returns true if the given string represents an integer, false

* otherwise.

*/

bool isinteger(char *str);

/*

* The parseint() function parses a well-formed string representation of

* an integer (one which would return true from isinteger()) and returns

* the integer value represented by the string. For example, the string

* "1234" would return the value 1234. This function does not need to

* handle badly-formed strings in any particular fashion, its operation

* on badly-formed strings is undefined.

* Returns the integer value stored in the given string.

*/

int parseint(char *str);

/*

* The main function is where C programs begin.

* This function parses its arguments and returns the value they

* represent. Its arguments are either:

* - A single argument representing an integer

* - Three arguments, where the first and third are integers and the

* second is an operator to be performed on those integers

* Remember that the argument in argv[0] is the name of the program, so

* a program passed exactly one argument on the command line will

* receive _two_ arguments: its name in argv[0] and the provided

* argument in argv[1].

* Arguments:

* argc - The number of arguments received

* argv - The arguments received as an array of C strings

*

* Returns 0 if the arguments are well-formed and the calculation could

* be performed, non-zero otherwise.

*/

int main(int argc, char *argv[]) {

/* Your main program logic should go here, with helper logic in the

* functions isinteger() and parseint(), which you can place below

* the closing brace of main() */

return 0;

}

Answer 1

// do comment if any problem arises

//code

#include <stdio.h>

#include <stdbool.h>

//this function returns length of string

int length(char* str)

{

int i=0;

while(str[i]!='\0')

{

i++;

}

return i;

}

/*

* The isinteger() function examines the string given as its first

* argument, and returns true if and only if the string represents a

* well-formed integer. A well-formed integer consists only of an

* optional leading - followed by one or more decimal digits.

* Returns true if the given string represents an integer, false

* otherwise.

*/

bool isinteger(char *str)

{

int i=0;

while(str[i]!='\0')

{

//if any character is not between 0 to 9 then return false

if(!(str[i]>='0'&&str[i]<='9'))

return false;

i++;

}

return true;

}

/*

* The parseint() function parses a well-formed string representation of

* an integer (one which would return true from isinteger()) and returns

* the integer value represented by the string. For example, the string

* "1234" would return the value 1234. This function does not need to

* handle badly-formed strings in any particular fashion, its operation

* on badly-formed strings is undefined.

* Returns the integer value stored in the given string.

*/

int parseint(char *str)

{

int l=length(str);

int number=0;

int i=0;

while(str[i]!='\0')

{

int current=str[i]-'0';

number*=10;

number+=current;

i++;

}

return number;

}

/*

* The main function is where C programs begin.

* This function parses its arguments and returns the value they

* represent. Its arguments are either:

* - A single argument representing an integer

* - Three arguments, where the first and third are integers and the

* second is an operator to be performed on those integers

* Remember that the argument in argv[0] is the name of the program, so

* a program passed exactly one argument on the command line will

* receive _two_ arguments: its name in argv[0] and the provided

* argument in argv[1].

* Arguments:

* argc - The number of arguments received

* argv - The arguments received as an array of C strings

*

* Returns 0 if the arguments are well-formed and the calculation could

* be performed, non-zero otherwise.

*/

int main(int argc, char *argv[])

{

/* Your main program logic should go here, with helper logic in the

* functions isinteger() and parseint(), which you can place below

* the closing brace of main() */

if (argc == 2 && isinteger(argv[1]))

{

printf("%d", parseint(argv[1]));

return 0;

}

else if (argc == 4 && isinteger(argv[1]) && isinteger(argv[3]))

{

int first=parseint(argv[1]);

int second=parseint(argv[3]);

switch (argv[2][0])

{

case '*':

printf("%d",first*second);

break;

case '+':

printf("%d",first+second);

break;

case '-':

printf("%d",first-second);

break;

case '/':

printf("%d",first/second);

break;

default:

break;

}

return 0;

}

return -1;

}

Output: