7.19. Coding Practice

Q1

Question

A palindrome is a word, phrase, or sentence that reads the same forwards and backwards. Write a function is_palindrome that takes a string input as a parameter and returns a boolean that is true if the input is a palindrome and false otherwise. The tests skip non-alphanumeric characters (space, puncuation, etc).

Run and test your code!

Example cp_7_AC_1q

#include <cctype>
#include <iostream>
#include <string>


bool is_palindrome (std::string input) {
    // Write your implementation here.
}

Answer

Below is one way to implement the program. We use the isalpha function to ignore the non alphabetical characters. Then we continuously check to see if the letters in the front are equal to the ones in the back until we reach the middle of the string.

Example cp_7_AC_1a

#include <cctype>
#include <iostream>
#include <string>

bool is_palindrome (std::string input) {
    int front = 0;
    int back = input.size() - 1;
    while (front < back) {
        while (!std::isalpha(input[front])) {
            ++front;
        }
        while (!std::isalpha(input[back])) {
            --back;
        }
        if (input[front] != input[back]) {
            return false;
        }
        ++front;
        --back;
    }
    return true;
}

Q2

How much does Bubba love shrimp? Probably a lot. But how many times does the word "shrimp" come up in his monologue? Write a function count_word that counts the number of times a given word appears in a given string. count_word should take two strings input and word as parameters and return an int. Feel free to use the string_to_lower function we wrote earlier.

Example cp_7_AC_2q

#include <cctype>
#include <iostream>
#include <string>


void string_to_lower (string &input) {
   int i = 0;
   while (i < input.size()) {
       if (std::isalpha(input[i]) != 0 && std::isupper(input[i]) != 0) {
           input[i] = std::tolower(input[i]);
       }
       ++i;
   }
}

int count_word (string input, string word) {
    // Write your implementation here.
}

int main() {
    string quote =
        "Anyway, like I was sayin', shrimp is the fruit of the sea. You can "
        "barbecue it, boil it, broil it, bake it, saute it. Dey's uh, "
        "shrimp-kabobs, shrimp creole, shrimp gumbo. Pan fried, deep fried, "
        "stir-fried. There's pineapple shrimp, lemon shrimp, coconut shrimp, "
        "pepper shrimp, shrimp soup, shrimp stew, shrimp salad, shrimp and "
        "potatoes, shrimp burger, shrimp sandwich. That- that's about "
        "it.";
    cout << "Your output: " << count_word(quote, "shrimp") << ", Correct output: 14" << '\n';
}

Q3

Question

Write a void function censor_word that censors a given word from a given string and prints out the new string. censor_word should take two strings input and word as parameters and prints out input with every occurence of word censored with asterisks. For example, censor_word ("I really, really, really, really, really, really like you", "really") results in the following output:

I ******, ******, ******, ******, ******, ****** like you

Example cp_7_AC_3q

#include <iostream>
#include <string>
using std::string;

void censor_word (string input, string word) {
    // Write your implementation here.
}

int main() {
    censor_word ("I really, really, really, really, really, really like you", "really");
}

Answer

Below is one way to implement the program. We use a while loop to repeatedly search for instances of word in input. Once found, we replace the length of the word with asterisks.

Example cp_7_AC_3a

#include <iostream>
#include <string>
using std::string;

void censor_word(string input, string word) {
    int length = word.size();
    while (input.find(word) != std::string::npos) {
        int index = input.find(word);
        int i = 0;
        while (i < length) {
            input[index + i] = '*';
            ++i;
        }
    }
    std::cout << input;
}

int main() {
    censor_word ("I really, really, really, really, really, really like you", "really");
}

Q4

Write a void function remove_word that removes a given word from a given string and prints out the new string. remove_word should take two strings input and word as parameters and prints out input with every occurence of word removed. Use string concatenation and the C++ string function substr. substr takes two parameters, a starting index and a length. For example, if string greeting = "hello world", then greeting.substr(6, 5) returns the string "world". Test your function in main. The output should be:

Gucci , Gucci , Gucci , Gucci

Example cp_7_AC_4q

#include <iostream>
#include <string>

void remove_word (std::string input, std::string word) {
    // Write your implementation here.
}

int main() {
    remove_word ("Gucci gang, Gucci gang, Gucci gang, Gucci gang", "gang");
}

Q5

Question

ROT13 is a simple letter substitution cipher that shifts every letter forward by 13, looping around if necessary. For example, the letter 'a', 1st in the alphabet, becomes the letter 'n', 14th in the alphabet. The letter 'r', 18th in the alphabet, becomes the letter 'e', 5th in the alphabet. Since the alphabet has 26 letters and 13 is exactly half, a message encrypted using ROT13 can be decrypted by calling ROT13 on the encrypted message. Write the function rotate13, which takes a string input as a parameter and returns an encrypted string. Test your function in main.

Example cp_7_AC_5q

#include <cctype>
#include <iostream>
#include <string>

std::string rotate13 (std::string message) {
    // Write your implementation here.
}

int main() {
    using std::cout;
    string original = "Encrypt me then decrypt me!";
    string encrypted = rotate13 (original);
    string decrypted = rotate13 (encrypted);
    cout << "Original string: " << original << '\n';
    cout << "Encrypted string: " << encrypted << '\n';
    cout << "Decrypted string: " << decrypted << '\n';

    // Uncomment and run the code below once your function works!
    // string secret_message = "Pbatenghyngvbaf! Lbh'ir fhpprffshyyl vzcyrzragrq EBG13 naq qrpbqrq gur frperg zrffntr :)";
    // cout << rotate13 (secret_message) << '\n';
}

Answer

Below is one way to implement the rotate13 function. We use a while loop to go through all the letters in the string. If the letter is between 'a' and 'n' or 'A' and 'N', we use character operations to add 13 to each letter. Otherwise, we subtract 13 from each letter. We return the encrypted message at the end.

Example cp_7_AC_5a

#include <cctype>
#include <iostream>
#include <string>
using std::string;

string rotate13(string message) {
    size_t pos = 0;
    while (pos < message.size()) {
       char& letter = message[pos];
        if (std::isalpha(letter) != 0) {
           if ((std::islower(letter) != 0 && letter < 'n') ||
               (std::isupper(letter) != 0 && letter < 'N')) {
             letter = letter + 13;
           } else {
             letter = letter - 13;
           }
        }
        ++pos;
    }
    return message;
}

int main() {
    using std::cout;
    string original = "Encrypt me then decrypt me!";
    string encrypted = rotate13 (original);
    string decrypted = rotate13 (encrypted);
    cout << "Original string: " << original << '\n';
    cout << "Encrypted string: " << encrypted << '\n';
    cout << "Decrypted string: " << decrypted << '\n';

    string secret = "Pbatenghyngvbaf! Lbh'ir fhpprffshyyl vzcyrzragrq EBG13 naq qrpbqrq gur frperg zrffntr :)";
    cout << rotate13 (secret) << '\n';
}

Q6

Write the function reverse_word which takes a string input, reverses it, and returns the reversed string. Run and test your code!

Example cp_7_AC_6q

#include <string>

std::string reverse_word (std::string input) {
    // Write your implementation here.
}

Q7

Question

Write the function capitalize, which takes a string input as a parameter. capitalize capitalizes the first letter of every word, and returns the new string.

Example cp_7_AC_7q

#include <cctype>
#include <iostream>
#include <string>

std::string capitalize (std::string input) {
    // Write your implementation here.
}

int main() {
    std::cout << capitalize ("every word in this string should be capitalized!\n");
    std::cout << capitalize ("this String As well\n");
}

Answer

Below is one way to implement the capitalize function. We use a while loop to go through all the chars in the string. We capitalize the first character and all characters following a space using toupper. At the end, we return the string.

Example cp_7_AC_7a

#include <cctype>
#include <iostream>
#include <string>

std::string capitalize (std::string input) {
    size_t pos = 0;
    while (pos < input.size()) {
        if (pos == 0) {
            input[pos] = std::toupper(input[pos]);
        }
        else if (input[pos-1] == ' ') {
            input[pos] = std::toupper(input[pos]);
        }
        ++pos;
    }
    return input;
}

int main() {
    std::cout << capitalize ("every word in this string should be capitalized!\n");
    std::cout << capitalize ("this String As well\n");
}

Q8

Write the function count_vowels which takes a string input and returns the number of vowels in the string. For this exercvise, 'a', 'e', 'i', 'o', and 'u' are vowels. Run and test your code!

Example cp_7_AC_8q

#include <string>

int count_vowels (std::string input) {
   // Write your implementation here.
}

Q9

Question

Write the function longest_word, which takes a string input as a parameter. longest_word returns the words with the most letters in input. If there's a tie, return the first word. Use the substr function. Run and test your code!

Example cp_7_AC_9q

#include <string>

std::string longest_word (std::string input) {
    // Write your implementation here.
}

Answer

Below is one way to implement the longest_word function. We use a while loop to go through all the chars in the string. We use variables to keep track of the longest word, the longest amount of letters, and the length of the current word. We can determine the length of a word by counting the number of chars between spaces. If the length is greater than the max, length becomes the new max and we update the longest word. This keeps repeating until we reach the end of the string, and the longest word is returned.

Example cp_7_AC_9a

#include <string>

std::string longest_word (std::string input) {
    size_t pos = 0;
    std::string longest;
    int max_length = 0;
    while (pos < input.size()) {
        int word_length = 0;
        while (input[pos] != ' ' && pos < input.size()) {
            ++word_length;
            ++pos;
        }
        if (word_length > max_length) {
            max_length = word_length;
            longest = input.substr(pos - max_length, max_length);
        }
        ++pos;
    }
    return longest;
}

Q10

Camel case is the practice of writing phrases without spaces or punctuation, indicating the separation of words using capital letter. For example, "camel case" in camel case is "camelCase". Snake case is the practice of writing phrases where each space is replaced by an underscore. For example, "snake case" in snake case is "snake_case". Write the functions snake_to_camel and camel_to_snake. Each function takes a string input and returns the input using the other stylization. Feel free to use any string functions you'd like. Run and test your code!

Example cp_7_AC_10q

#include <string>
using std::string;

string snake_to_camel (string input) {
     // Write your implementation here.
}

string camel_to_snake (string input) {
     // Write your implementation here.
}