add 56

src/euler56/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "euler56"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+rug = "1.17.0"

src/euler56/src/main.rs

@@ -0,0 +1,41 @@
+use rug::{ops::Pow, Integer};
+
+fn main() {
+    let mut solution = vec![];
+    for a in 1..100 {
+        for b in 1..100 {
+            let aa = Integer::from(a);
+            let result = digital_sum(aa.pow(b));
+            println!("{result}");
+            solution.push(result);
+        }
+    }
+    let max = solution.into_iter().max().unwrap();
+    println!("{}", max);
+}
+
+fn digital_sum(int: Integer) -> u32 {
+    int.to_string()
+        .chars()
+        .map(|c| c.to_digit(10).unwrap() as u32)
+        .sum()
+}
+
+#[cfg(test)]
+mod test {
+    use super::digital_sum;
+    use rug::ops::Pow;
+    use rug::Integer;
+
+    #[test]
+    fn test_digital_sum() {
+        let result = digital_sum(Integer::from(100).pow(100));
+        assert_eq!(result, 1);
+
+        let result = digital_sum(Integer::from(5).pow(2));
+        assert_eq!(result, 7);
+
+        let result = digital_sum(Integer::from(6).pow(2));
+        assert_eq!(result, 9);
+    }
+}