Add problem 3206: Alternating Groups I

Author: EFanZh

src/lib.rs

@@ -2135,6 +2135,7 @@ pub mod problem_3195_find_the_minimum_area_to_cover_all_ones_i;
 pub mod problem_3196_maximize_total_cost_of_alternating_subarrays;
 pub mod problem_3200_maximum_height_of_a_triangle;
 pub mod problem_3201_find_the_maximum_length_of_valid_subsequence_i;
+pub mod problem_3206_alternating_groups_i;
 pub mod problem_3350_adjacent_increasing_subarrays_detection_ii;
 
 #[cfg(test)]

src/problem_3206_alternating_groups_i/iterative.rs

@@ -0,0 +1,35 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl Solution {
+    pub fn number_of_alternating_groups(colors: Vec<i32>) -> i32 {
+        assert!(colors.len() > 2);
+
+        let mut state = (colors[colors.len() - 2] << 1) | colors[colors.len() - 1];
+        let mut result = 0;
+
+        for color in colors {
+            state = (state << 1) | color;
+            result += i32::from(matches!(state & 0b_111, 0b_010 | 0b_101));
+        }
+
+        result
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn number_of_alternating_groups(colors: Vec<i32>) -> i32 {
+        Self::number_of_alternating_groups(colors)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}

src/problem_3206_alternating_groups_i/mod.rs

@@ -0,0 +1,18 @@
+pub mod iterative;
+
+pub trait Solution {
+    fn number_of_alternating_groups(colors: Vec<i32>) -> i32;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    pub fn run<S: Solution>() {
+        let test_cases = [(&[1, 1, 1] as &[_], 0), (&[0, 1, 0, 0, 1], 3)];
+
+        for (colors, expected) in test_cases {
+            assert_eq!(S::number_of_alternating_groups(colors.to_vec()), expected);
+        }
+    }
+}