In this challenge, you will demonstrate your understanding of control flow in Rust. The task involves finding the first decimal palindrome in a given range.

What's a decimal palindrome?

A decimal palindrome is a number whose decimal (base 10, "normal") digits read the same backward as forward. This exercise will require you to find the numerically least non-negative palindrome in a given range. The easiest way to do this is to iterate through the range, check each number to see if it is a palindrome, and return the first palindrome found. You can use any control flow construct to solve this problem. (There are much more efficient ways to solve this problem, but the calculations get complex quickly.)

Palindromes are fascinating numbers, and finding them within a range will require clear control flow logic to ensure you identify the first one accurately.

Your task

You need to write a function, find_first_palindrome(start: i32, end: i32) -> Option<i32>, that takes two integer arguments start and end. The function should return the numerically least non-negative palindrome number within the range.

• The range is inclusive: for example, if start == 1 and end == 1 the palindrome 1 is in range.

• The range may have start > end, in which case it is still a valid range: for example, start == 3 and end == 1 contains the values 1, 2, 3.

If there are no palindromes in the range, the function should return None.

Requirements

• The function should cover the numbers from start to end inclusive.
• It should check each non-negative number to determine if it is a palindrome.
• The function should return the numerically least palindrome found, or None if no palindromes exist in the range.
• You must handle "reversed" ranges, when start is greater than end.

Example

let result = find_first_palindrome(10, 30);
assert_eq!(result, Some(11)); // 11 is the first palindrome in the range

let result = find_first_palindrome(100, 105);
assert_eq!(result, Some(101)); // 101 is the first palindrome in the range

let result = find_first_palindrome(123, 130);
assert_eq!(result, None); // No palindromes in this range

let result = find_first_palindrome(-130, -1);
assert_eq!(result, None); // No palindromes in this range

let result = find_first_palindrome(100, -105);
assert_eq!(result, Some(0)); // 0 is the first palindrome in the range

Did you know?

Did you know that palindromes are not just limited to numbers? They are found in words, phrases, and even DNA sequences! For example, the word "racecar" is a palindrome, as it reads the same backward and forward. Check out this "Weird Al" video for many many examples.

Palindromes are fascinating in various fields, including mathematics, literature, and biology, where they often have unique properties and significance.

Hints

• To check if a number is a palindrome, you probably want to convert it to a String and compare it with its reverse.
• You can get the chars in a String by using the chars() method on a String
• You can iterate over values in reverse order by using the rev() method on an iterator. For example, you can get the chars in a String s in reverse order with s.chars().rev()
• Use a loop, iterator, or any other control flow construct to check each number in the range until a palindrome is found or the range is exhausted.
• Remember to handle the case where start is greater than end, probably by swapping the values if necessary.