20250107 finished.

src/problem/mod.rs

@@ -416,3 +416,5 @@ mod p732_my_calendar_iii;
 mod p2241_design_an_atm_machine;
 
 mod p2274_maximum_consecutive_floors_without_special_floors;
+
+mod p3019_number_of_changing_keys;

src/problem/p3019_number_of_changing_keys.rs

@@ -0,0 +1,37 @@
+/**
+ * [3019] Number of Changing Keys
+ */
+pub struct Solution {}
+
+// submission codes start here
+
+impl Solution {
+    pub fn count_key_changes(s: String) -> i32 {
+        let mut second_chars = s.chars();
+        second_chars.next();
+
+        second_chars
+            .zip(s.chars())
+            .filter_map(|(a, b)| {
+                if a.to_lowercase().next() != b.to_lowercase().next() {
+                    Some(())
+                } else {
+                    None
+                }
+            })
+            .count() as i32
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_3019() {
+        assert_eq!(2, Solution::count_key_changes("aAbBcC".to_owned()));
+        assert_eq!(0, Solution::count_key_changes("AaAaAaaA".to_owned()));
+    }
+}