add 55

src/euler55/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "euler55"
+version = "0.1.0"
+edition = "2021"
+
+
+
+[dependencies]
+
+

src/euler55/src/main.rs

@@ -0,0 +1,71 @@
+type Int = u128;
+
+const MAX_VALUE: Int = 10_000;
+const NUMBER_CASES: Int = MAX_VALUE - 1;
+
+fn main() {
+    let mut lychrel_count = NUMBER_CASES;
+    let numbers: Vec<_> = (1..MAX_VALUE).into_iter().collect();
+    for n in numbers {
+        let mut accum = n;
+        for _ in 0..50 {
+            accum += reverse_number(accum);
+            if is_palindrome(accum) {
+                lychrel_count -= 1;
+                break;
+            }
+        }
+    }
+
+    println!("{lychrel_count}");
+}
+
+fn reverse_number(x: Int) -> Int {
+    x.to_string()
+        .chars()
+        .rev()
+        .collect::<String>()
+        .parse()
+        .unwrap()
+}
+
+fn is_palindrome(x: Int) -> bool {
+    let c1 = x.to_string();
+    let c2 = c1.chars().rev().collect::<String>();
+    c1 == c2
+}
+
+#[cfg(test)]
+mod test {
+    use crate::{is_palindrome, reverse_number};
+
+    #[test]
+    fn test_palindrome() {
+        assert!(is_palindrome(121));
+        assert!(!is_palindrome(120));
+        assert!(is_palindrome(123454321));
+    }
+
+    #[test]
+    fn test_reverse_number() {
+        assert_eq!(reverse_number(12345), 54321);
+    }
+
+    #[test]
+    fn test_iteration() {
+        let mut accum = 349;
+        for _ in 0..3 {
+            accum += reverse_number(accum);
+        }
+        assert_eq!(accum, 7337);
+    }
+
+    #[test]
+    fn test_196() {
+        let mut accum = 196;
+        for _ in 0..50 {
+            accum += reverse_number(accum);
+        }
+        assert!(!is_palindrome(accum));
+    }
+}