Solution 4

src/bin/problem_4.rs

@@ -0,0 +1,42 @@
+fn main() {
+    let result = find_largest_palindrome(3);
+    println!("Result: {}", result);
+}
+
+fn find_largest_palindrome(digits: u32) -> i64 {
+    let mut largest = 0;
+    let lower = 10_i64.pow(digits - 1);
+    let upper = 10_i64.pow(digits);
+    for i in lower..upper {
+        for j in lower..upper {
+            let product = i * j;
+            if check_palindrome(product) && product > largest {
+                largest = product;
+            }
+        }
+    }
+
+    return largest;
+}
+
+fn check_palindrome(number: i64) -> bool {
+    let number: Vec<char> = number.to_string().chars().collect();
+    let upper = (number.len() as f64 / 2.0).ceil() as usize;
+    for pos in 0..upper {
+        if number[pos] != number[number.len() - 1 - pos] {
+            return false;
+        }
+    }
+    return true;
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::find_largest_palindrome;
+
+    #[test]
+    fn it_works() {
+        let result = find_largest_palindrome(2);
+        assert_eq!(result, 9009);
+    }
+}