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src/euler38/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "euler38"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+
+[profile.release]
+lto = "thin"
+debug = true

src/euler38/src/main.rs

@@ -0,0 +1,52 @@
+fn main() {
+    let mut largest_number = 0;
+    let mut largest_string = String::new();
+    let mut string = String::new();
+    for integer in 1..=500_000_000_usize {
+        string.clear();
+        for factor in 1.. {
+            let number = integer * factor;
+            string.push_str(&number.to_string());
+            let as_number = string.parse::<usize>().unwrap();
+
+            if correct_length(&string) && as_number > largest_number && is_pandigital(&string) {
+                largest_number = as_number;
+                largest_string = string.clone();
+                break;
+            }
+            if too_large(&string) {
+                break;
+            }
+        }
+    }
+    println!("{largest_string}");
+}
+
+fn is_pandigital(s: &str) -> bool {
+    for c in '1'..='9' {
+        if !s.contains(c) {
+            return false;
+        }
+    }
+    true
+}
+
+fn correct_length(s: &str) -> bool {
+    s.len() == 9
+}
+
+fn too_large(s: &str) -> bool {
+    s.len() > 9
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::is_pandigital;
+
+    #[test]
+    fn test_pandigital() {
+        assert!(is_pandigital(&192384576.to_string()));
+        assert!(is_pandigital(&918273645.to_string()));
+        assert!(!is_pandigital(&9.to_string()));
+    }
+}