Add problem 2266: Count Number of Texts

src/lib.rs

@@ -1557,6 +1557,7 @@ pub mod problem_2259_remove_digit_from_number_to_maximize_result;
 pub mod problem_2260_minimum_consecutive_cards_to_pick_up;
 pub mod problem_2264_largest_3_same_digit_number_in_string;
 pub mod problem_2265_count_nodes_equal_to_average_of_subtree;
+pub mod problem_2266_count_number_of_texts;
 pub mod problem_2270_number_of_ways_to_split_array;
 
 #[cfg(test)]

src/problem_2266_count_number_of_texts/dynamic_programming.rs

@@ -0,0 +1,68 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl Solution {
+    fn add(target: &mut u32, value: u32) {
+        *target += value;
+        *target = target.checked_sub(1_000_000_007).unwrap_or(*target);
+    }
+
+    pub fn count_texts(pressed_keys: String) -> i32 {
+        let mut cache = [1_u32; 4];
+        let mut head = 0;
+        let mut prev = 0;
+        let mut length_minus_1 = u8::MAX;
+
+        for c in pressed_keys.bytes() {
+            if c == prev {
+                length_minus_1 = length_minus_1.wrapping_add(1).min(3);
+            } else {
+                prev = c;
+                length_minus_1 = 0;
+            }
+
+            let mut count = cache[head & 3];
+
+            'block_0: {
+                'block_1: {
+                    match length_minus_1 {
+                        0 => break 'block_0,
+                        1 => break 'block_1,
+                        2 => {}
+                        _ => {
+                            if matches!(prev, b'7' | b'9') {
+                                Self::add(&mut count, cache[head.wrapping_add(3) & 3]);
+                            }
+                        }
+                    }
+
+                    Self::add(&mut count, cache[head.wrapping_add(2) & 3]);
+                }
+
+                Self::add(&mut count, cache[head.wrapping_add(1) & 3]);
+            }
+
+            head = head.wrapping_sub(1);
+            cache[head & 3] = count;
+        }
+
+        cache[head & 3] as _
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn count_texts(pressed_keys: String) -> i32 {
+        Self::count_texts(pressed_keys)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}

src/problem_2266_count_number_of_texts/mod.rs

@@ -0,0 +1,18 @@
+pub mod dynamic_programming;
+
+pub trait Solution {
+    fn count_texts(pressed_keys: String) -> i32;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    pub fn run<S: Solution>() {
+        let test_cases = [("22233", 8), ("222222222222222222222222222222222222", 82_876_089)];
+
+        for (pressed_keys, expected) in test_cases {
+            assert_eq!(S::count_texts(pressed_keys.to_string()), expected);
+        }
+    }
+}