Add a new solution to problem 2241: Design an ATM Machine

src/problem_2241_design_an_atm_machine/greedy_2.rs

@@ -0,0 +1,80 @@
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+use std::convert::TryInto;
+
+#[allow(clippy::struct_field_names, clippy::upper_case_acronyms)]
+pub struct ATM {
+    counts: [u32; 5],
+}
+
+impl ATM {
+    fn new() -> Self {
+        Self { counts: [0; 5] }
+    }
+
+    pub fn deposit(&mut self, banknotes_count: Vec<i32>) {
+        let banknotes_count: &[_; 5] = banknotes_count.as_slice().try_into().ok().unwrap();
+
+        for (target, &count) in self.counts.iter_mut().zip(banknotes_count) {
+            *target += count as u32;
+        }
+    }
+
+    pub fn withdraw(&mut self, amount: i32) -> Vec<i32> {
+        let mut amount = amount as u32;
+        let mut result = vec![0; 5];
+        let result_ref: &mut [_; 5] = result.as_mut_slice().try_into().ok().unwrap();
+
+        let mut iter = result_ref
+            .iter_mut()
+            .zip([20, 50, 100, 200, 500].iter().zip(&self.counts));
+
+        loop {
+            if let Some((target, (&base, &available))) = iter.next_back() {
+                let count = (amount / base).min(available);
+
+                *target = count as _;
+                amount -= base * count;
+
+                if amount != 0 {
+                    continue;
+                }
+
+                for (available, required) in self.counts.iter_mut().zip(&*result_ref) {
+                    *available -= *required as u32;
+                }
+            } else {
+                result_ref[0] = -1;
+                result.truncate(1);
+            }
+
+            break;
+        }
+
+        result
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::ATM for ATM {
+    fn new() -> Self {
+        Self::new()
+    }
+
+    fn deposit(&mut self, banknotes_count: Vec<i32>) {
+        self.deposit(banknotes_count);
+    }
+
+    fn withdraw(&mut self, amount: i32) -> Vec<i32> {
+        self.withdraw(amount)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::ATM>();
+    }
+}

src/problem_2241_design_an_atm_machine/mod.rs

@@ -1,4 +1,5 @@
 pub mod greedy;
+pub mod greedy_2;
 
 #[allow(clippy::upper_case_acronyms)] // Expected.
 pub trait ATM {