Add problem 3121: Count the Number of Special Characters II

Author: EFanZh

src/lib.rs

@@ -2096,6 +2096,7 @@ pub mod problem_3111_minimum_rectangles_to_cover_points;
 pub mod problem_3114_latest_time_you_can_obtain_after_replacing_characters;
 pub mod problem_3115_maximum_prime_difference;
 pub mod problem_3120_count_the_number_of_special_characters_i;
+pub mod problem_3121_count_the_number_of_special_characters_ii;
 pub mod problem_3350_adjacent_increasing_subarrays_detection_ii;
 
 #[cfg(test)]

src/problem_3121_count_the_number_of_special_characters_ii/bit_manipulation.rs

@@ -0,0 +1,34 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl Solution {
+    pub fn number_of_special_chars(word: String) -> i32 {
+        let state = word.into_bytes().into_iter().fold(0_u64, |state, c| {
+            let shift = (c & 31) * 2;
+            let transition = ((0b_0110_0110_u64 << 32) | 0b_1111_0101_u64) >> (c & 32);
+            let new_state = transition >> (((state >> shift) & 0b_11) * 2);
+            let mask = 0b_11 << shift;
+
+            (state & !mask) | ((new_state << shift) & mask)
+        });
+
+        (state & (state >> 1) & 0x_5555_5555_5555_5555).count_ones() as _
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn number_of_special_chars(word: String) -> i32 {
+        Self::number_of_special_chars(word)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}

src/problem_3121_count_the_number_of_special_characters_ii/mod.rs

@@ -0,0 +1,18 @@
+pub mod bit_manipulation;
+
+pub trait Solution {
+    fn number_of_special_chars(word: String) -> i32;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    pub fn run<S: Solution>() {
+        let test_cases = [("aaAbcBC", 3), ("abc", 0), ("AbBCab", 0)];
+
+        for (word, expected) in test_cases {
+            assert_eq!(S::number_of_special_chars(word.to_string()), expected);
+        }
+    }
+}