Add problem 2094: Finding 3-Digit Even Numbers

src/lib.rs

@@ -1523,6 +1523,7 @@ pub mod problem_2087_minimum_cost_homecoming_of_a_robot_in_a_grid;
 pub mod problem_2089_find_target_indices_after_sorting_array;
 pub mod problem_2090_k_radius_subarray_averages;
 pub mod problem_2091_removing_minimum_and_maximum_from_array;
+pub mod problem_2094_finding_3_digit_even_numbers;
 pub mod problem_2095_delete_the_middle_node_of_a_linked_list;
 pub mod problem_2099_find_subsequence_of_length_k_with_the_largest_sum;
 pub mod problem_2103_rings_and_rods;

src/problem_2094_finding_3_digit_even_numbers/brute_force.rs

@@ -0,0 +1,62 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+use std::cell::Cell;
+
+impl Solution {
+    pub fn find_even_numbers(digits: Vec<i32>) -> Vec<i32> {
+        #[allow(clippy::declare_interior_mutable_const)] // TODO: Use inline
+        const ZERO_CELL: Cell<u8> = Cell::new(0);
+
+        let mut counts = [ZERO_CELL; 10];
+
+        for digit in digits {
+            *counts[digit as u32 as usize].get_mut() += 1;
+        }
+
+        let mut result = Vec::new();
+
+        for candidate in (100_u32..1000).step_by(2) {
+            let first_count = &counts[(candidate / 100) as usize];
+
+            if first_count.get() != 0 {
+                first_count.set(first_count.get() - 1);
+
+                let second_count = &counts[((candidate / 10) % 10) as usize];
+
+                if second_count.get() != 0 {
+                    second_count.set(second_count.get() - 1);
+
+                    let third_count = &counts[(candidate % 10) as usize];
+
+                    if third_count.get() != 0 {
+                        result.push(candidate as _);
+                    }
+
+                    second_count.set(second_count.get() + 1);
+                }
+
+                first_count.set(first_count.get() + 1);
+            }
+        }
+
+        result
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn find_even_numbers(digits: Vec<i32>) -> Vec<i32> {
+        Self::find_even_numbers(digits)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}

src/problem_2094_finding_3_digit_even_numbers/brute_force_2.rs

@@ -0,0 +1,68 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+use std::cell::Cell;
+
+impl Solution {
+    pub fn find_even_numbers(digits: Vec<i32>) -> Vec<i32> {
+        #[allow(clippy::declare_interior_mutable_const)] // TODO: Use inline
+        const ZERO_CELL: Cell<u8> = Cell::new(0);
+
+        let mut counts = [ZERO_CELL; 10];
+
+        for digit in digits {
+            *counts[digit as u32 as usize].get_mut() += 1;
+        }
+
+        let mut result = Vec::new();
+
+        for first in 1..10 {
+            let first_count = &counts[first];
+
+            if first_count.get() != 0 {
+                let value = first as i32 * 100;
+
+                first_count.set(first_count.get() - 1);
+
+                for second in 0..10 {
+                    let second_count = &counts[second];
+
+                    if second_count.get() != 0 {
+                        let value = value + second as i32 * 10;
+
+                        second_count.set(second_count.get() - 1);
+
+                        for third in (0..10).step_by(2) {
+                            if counts[third].get() != 0 {
+                                result.push(value + third as i32);
+                            }
+                        }
+
+                        second_count.set(second_count.get() + 1);
+                    }
+                }
+
+                first_count.set(first_count.get() + 1);
+            }
+        }
+
+        result
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn find_even_numbers(digits: Vec<i32>) -> Vec<i32> {
+        Self::find_even_numbers(digits)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}

src/problem_2094_finding_3_digit_even_numbers/mod.rs

@@ -0,0 +1,26 @@
+pub mod brute_force;
+pub mod brute_force_2;
+
+pub trait Solution {
+    fn find_even_numbers(digits: Vec<i32>) -> Vec<i32>;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    pub fn run<S: Solution>() {
+        let test_cases = [
+            (
+                &[2, 1, 3, 0] as &[_],
+                &[102, 120, 130, 132, 210, 230, 302, 310, 312, 320] as &[_],
+            ),
+            (&[2, 2, 8, 8, 2], &[222, 228, 282, 288, 822, 828, 882]),
+            (&[3, 7, 5], &[]),
+        ];
+
+        for (digits, expected) in test_cases {
+            assert_eq!(S::find_even_numbers(digits.to_vec()), expected);
+        }
+    }
+}