20250119 finished.

src/problem/mod.rs

@@ -440,3 +440,5 @@ mod p3095_shortest_subarray_with_or_at_least_k_i;
 mod p3097_shortest_subarray_with_or_at_least_k_ii;
 
 mod p3287_find_the_maximum_sequence_value_of_array;
+
+mod p2266_count_number_of_texts;

src/problem/p2266_count_number_of_texts.rs

@@ -0,0 +1,92 @@
+/**
+ * [2266] Count Number of Texts
+ */
+pub struct Solution {}
+
+// submission codes start here
+use std::collections::HashSet;
+
+const MODE: i64 = 1_000_000_007;
+
+impl Solution {
+    pub fn count_texts(pressed_keys: String) -> i32 {
+        let three_keys = HashSet::from(['2', '3', '4', '5', '6', '8']);
+        let pressed_keys: Vec<char> = pressed_keys.chars().collect();
+
+        let mut three_dp = Vec::from([0, 1, 2, 4]);
+        let mut four_dp = Vec::from([0, 1, 2, 4, 8]);
+
+        let mut get_three = |n: usize| {
+            if n >= three_dp.len() {
+                for i in three_dp.len()..=n {
+                    three_dp.push((three_dp[i - 1] + three_dp[i - 2] + three_dp[i - 3]) % MODE);
+                }
+            }
+
+            three_dp[n]
+        };
+
+        let mut get_four = |n: usize| {
+            if n >= four_dp.len() {
+                for i in four_dp.len()..=n {
+                    four_dp.push(
+                        (four_dp[i - 1] + four_dp[i - 2] + four_dp[i - 3] + four_dp[i - 4]) % MODE,
+                    );
+                }
+            }
+
+            four_dp[n]
+        };
+
+        let mut last_key = None;
+        let mut count = 0;
+        let mut result = 1;
+
+        for c in pressed_keys {
+            if let Some(last) = last_key {
+                if last == c {
+                    count += 1;
+                } else {
+                    if three_keys.contains(&last) {
+                        result = result * get_three(count) % MODE;
+                    } else {
+                        result = result * get_four(count) % MODE;
+                    }
+
+                    last_key = Some(c);
+                    count = 1;
+                }
+            } else {
+                last_key = Some(c);
+                count = 1;
+            }
+        }
+
+        if let Some(last) = last_key {
+            if three_keys.contains(&last) {
+                result = result * get_three(count) % MODE;
+            } else {
+                result = result * get_four(count) % MODE;
+            }
+        }
+
+        result as i32
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_2266() {
+        assert_eq!(3136, Solution::count_texts("444479999555588866".to_owned()));
+        assert_eq!(8, Solution::count_texts("22233".to_owned()));
+        assert_eq!(
+            82876089,
+            Solution::count_texts("222222222222222222222222222222222222".to_owned())
+        );
+    }
+}