Parsing numeric arguments - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to convert the string argument to an integer using atoi.

C

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[]) {
    if (argc < 2) {
        printf("Please provide a number.\n");
        return 1;
    }
    int num = [1](argv[1]);
    printf("Number is %d\n", num);
    return 0;
}

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Aatoi

Bstrlen

Cprintf

Dscanf

Attempts:

3 left

💡 Hint

Common Mistakes

Using printf instead of atoi.

Using strlen which returns string length, not number.

Using scanf incorrectly here.

The function atoi converts a string to an integer. Here, argv[1] is the string argument to convert.

2fill in blank

medium

Complete the code to parse a long integer from the string argument using strtol.

C

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[]) {
    if (argc < 2) {
        printf("Please provide a number.\n");
        return 1;
    }
    char *endptr;
    long val = [1](argv[1], &endptr, 10);
    if (*endptr != '\0') {
        printf("Invalid number: %s\n", argv[1]);
        return 1;
    }
    printf("Parsed long: %ld\n", val);
    return 0;
}

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Astrcpy

Bstrlen

Catoi

Dstrtol

Attempts:

3 left

💡 Hint

Common Mistakes

Using atoi which does not detect invalid characters.

Using strcpy which copies strings but does not convert.

Using strlen which returns length, not number.

strtol converts a string to a long integer and allows error checking via endptr.

3fill in blank

hard

Fix the error in the code to correctly parse a double from the string argument using strtod.

C

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[]) {
    if (argc < 2) {
        printf("Please provide a number.\n");
        return 1;
    }
    char *endptr;
    double val = [1](argv[1], &endptr);
    if (*endptr != '\0') {
        printf("Invalid number: %s\n", argv[1]);
        return 1;
    }
    printf("Parsed double: %f\n", val);
    return 0;
}

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Astrtol

Bstrtod

Catoi

Datof

Attempts:

3 left

💡 Hint

Common Mistakes

Using atof which does not allow error checking.

Using atoi which converts to int, not double.

Using strtol which converts to long, not double.

strtod converts a string to a double and allows error checking via endptr.

4fill in blank

hard

Fill both blanks to create a dictionary-like structure that maps argument index to its parsed integer value if the argument is numeric.

C

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>

int is_number(const char *s) {
    while (*s) {
        if (![2](*s)) return 0;
        s++;
    }
    return 1;
}

int main(int argc, char *argv[]) {
    for (int i = 1; i < argc; i++) {
        if (is_number(argv[i])) {
            int val = [1](argv[i]);
            printf("Arg %d is number %d\n", i, val);
        } else {
            printf("Arg %d is not a number\n", i);
        }
    }
    return 0;
}

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Aatoi

Bstrtol

Cisdigit

Dprintf

Attempts:

3 left

💡 Hint

Common Mistakes

Using strtol without proper error checking.

Using printf instead of conversion function.

Using isdigit on whole string instead of characters.

atoi converts string to int; isdigit checks if a character is a digit.

5fill in blank

hard

Fill all three blanks to parse command line arguments as integers, check for errors, and print the sum.

C

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[]) {
    int sum = 0;
    for (int i = 1; i < argc; i++) {
        char *endptr;
        int val = (int)[1](argv[i], &[2], 10);
        if (*[3] != '\0') {
            printf("Invalid number: %s\n", argv[i]);
            return 1;
        }
        sum += val;
    }
    printf("Sum is %d\n", sum);
    return 0;
}

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Astrtol

Bendptr

Datoi

Attempts:

3 left

💡 Hint

Common Mistakes

Using atoi which does not allow error checking.

Not checking endptr to detect invalid input.

Confusing variable names for endptr.

strtol parses string to long with error checking via endptr pointer.