add 52

src/euler52/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "euler52"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

src/euler52/src/main.rs

@@ -0,0 +1,63 @@
+use std::collections::HashMap;
+
+const MULTIPLES_TO_CHECK: [u64; 5] = [2, 3, 4, 5, 6];
+
+fn main() {
+    let mut i = 10;
+
+    'outer: loop {
+        i += 1;
+        let hm1 = get_amount_of_digits(i);
+        for factor in MULTIPLES_TO_CHECK {
+            let double = i * factor;
+            let hm2 = get_amount_of_digits(double);
+            if hm1 != hm2 {
+                continue 'outer;
+            }
+        }
+        break;
+    }
+    println!("{i}");
+}
+
+fn get_amount_of_digits(i: u64) -> HashMap<u64, usize> {
+    let mut result = get_empty_hashmap();
+    i.to_string()
+        .chars()
+        .map(|c| c.to_digit(10).unwrap() as u64)
+        .for_each(|d| {
+            result.insert(d, result[&d] + 1);
+        });
+    result
+}
+
+fn get_empty_hashmap() -> HashMap<u64, usize> {
+    let mut hm = HashMap::new();
+    for i in 0..10 {
+        hm.insert(i, 0);
+    }
+    hm
+}
+
+#[cfg(test)]
+mod test {
+    use crate::{get_amount_of_digits, get_empty_hashmap};
+
+    #[test]
+    fn test_get_amount_of_digits() {
+        let mut correct = get_empty_hashmap();
+        correct.insert(2, 1);
+        correct.insert(5, 2);
+        correct.insert(0, 1);
+        assert_eq!(correct, get_amount_of_digits(5250));
+    }
+
+    #[test]
+    fn test_get_empty_hashmap() {
+        let hm = get_empty_hashmap();
+        assert_eq!(hm.len(), 10);
+        for (_, v) in hm {
+            assert_eq!(v, 0);
+        }
+    }
+}