20250131 finished.

src/problem/mod.rs

@@ -460,3 +460,5 @@ mod p40_combination_sum_ii;
 mod p119_pascals_triangle_ii;
 
 mod p350_intersection_of_two_arrays_ii;
+
+mod p541_reverse_string_ii;

src/problem/p541_reverse_string_ii.rs

@@ -0,0 +1,64 @@
+/**
+ * [541] Reverse String II
+ */
+pub struct Solution {}
+
+// submission codes start here
+
+impl Solution {
+    pub fn reverse_str(s: String, k: i32) -> String {
+        let s: Vec<char> = s.chars().collect();
+
+        let mut reverse = true;
+        let k = k as usize;
+
+        let mut result = Vec::with_capacity(s.len());
+        let mut buffer = Vec::with_capacity(k);
+        let mut pos = 0;
+
+        'outer: loop {
+            for _ in 0..k {
+                if pos == s.len() {
+                    while let Some(c) = buffer.pop() {
+                        result.push(c);
+                    }
+
+                    break 'outer;
+                }
+
+                if reverse {
+                    buffer.push(s[pos]);
+                } else {
+                    result.push(s[pos]);
+                }
+                pos += 1;
+            }
+
+            while let Some(c) = buffer.pop() {
+                result.push(c);
+            }
+            reverse = !reverse;
+        }
+
+        result.into_iter().collect()
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_541() {
+        assert_eq!(
+            "bacdfeg".to_owned(),
+            Solution::reverse_str("abcdefg".to_owned(), 2)
+        );
+        assert_eq!(
+            "bacd".to_owned(),
+            Solution::reverse_str("abcd".to_owned(), 2)
+        );
+    }
+}