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For the 2018-2019 school year, we have switched to using the WLMOJ judge for lesson information, no new lessons will be added here.

In this lesson, we will be focusing on the syntax of using variables.


Turing

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var myStr : string := "hello"

put(myStr) % Print myStr.
put(myStr(1)) % Print the first character in myStr.
put(myStr(*)) % Print the last character in myStr.
put(myStr(* - 1)) % Print the second last character in myStr.

Python

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myStr = "hello"

print(myStr) # Print myStr.
print(myStr[0]) # Print the first character in myStr.
print(myStr[-1]) # Print the last character in myStr.
print(myStr[-2]) # Print the second last character in myStr.

Java

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/*
 * Strings in Java are objects.
 * This will be explained further in later lessons.
 * For now, just know that when you declare an object, the variable type is capitalized.
 */
String myStr = "hello";

System.out.println(myStr); // Print myStr.
System.out.println(myStr.charAt(0)); // Print the first character in myStr.
System.out.println(myStr.charAt(myStr.length() - 1)); // Print the last character in myStr.
System.out.println(myStr.charAt(myStr.length() - 2)); // Print the second last character in myStr.

When dealing with strings, you will often have to manipulate them. Reversing strings is a good exercise to practice doing this.

Turing

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var original : string := "123" % This is the string we will reverse.
var reversed : string := "" % Create an empty string. We will add the characters in reverse order next.

for decreasing i : length (original) .. 1 % Loop through the original string backwards.
    reversed += original(i); % Add the characters one by one.
end for

put(original + " backwards is: " + reversed) % Print the final result.

Python

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original = "123" # This is the string we will reverse.
reversedString = "" # Create an empty string. We will add the characters in reverse order next.

for c in reversed(original): # Loop through the characters in the original string backwards.
	reversedString += c

print (reversedString) # Print the final result.

# This is another way to reverse string in Python.
# While this method is faster, it make no sense unless you are familiar with Python.
# This way also defeats the purpose of this exercise, which is to show the process of solving string manipulation problems.
print (original[::-1])

Java

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String original = "123";
String reversed = "";

for (int i = original.length() - 1; i >= 0; i--) {
	reversed += original.charAt(i);
}

System.out.println(reversed);

You can do a lot with strings, and will use them a lot throughout your programming. It is important that you understand and are comfortable with using and manipulating strings.

Practice

Palindromes

One of the most basic string manipulation problems.

Write a program that tells the user if a string they enter is a palindrome. Ignore spaces, punctuation, and capitalization.

A palindrome is a string that is the same if you reverse it.

Examples of palindromes are: “Anna”, “A man, a plan, a canal, Panama!”, and “taco cat”.

Capitalization

Write a program to fix the capitalization of sentences.

If the user inputs: “this sentence is capitalized wrong. so is this! This one is right.”

Your program should output: “This sentence is capitalized wrong. So is this! This one is right.”