Add problem 3216: Lexicographically Smallest String After a Swap

Author: EFanZh

src/lib.rs

@@ -2140,6 +2140,7 @@ pub mod problem_3208_alternating_groups_ii;
 pub mod problem_3210_find_the_encrypted_string;
 pub mod problem_3211_generate_binary_strings_without_adjacent_zeros;
 pub mod problem_3212_count_submatrices_with_equal_frequency_of_x_and_y;
+pub mod problem_3216_lexicographically_smallest_string_after_a_swap;
 pub mod problem_3350_adjacent_increasing_subarrays_detection_ii;
 
 #[cfg(test)]

src/problem_3216_lexicographically_smallest_string_after_a_swap/greedy.rs

@@ -0,0 +1,42 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+use std::mem;
+
+impl Solution {
+    pub fn get_smallest_string(s: String) -> String {
+        let mut s = s.into_bytes();
+        let mut iter = s.iter_mut();
+        let mut zero = 0;
+        let mut prev = iter.next().unwrap_or(&mut zero);
+
+        for value in iter {
+            if *value < *prev && (*prev ^ *value) & 1 == 0 {
+                mem::swap(prev, value);
+
+                break;
+            }
+
+            prev = value;
+        }
+
+        String::from_utf8(s).unwrap()
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn get_smallest_string(s: String) -> String {
+        Self::get_smallest_string(s)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}

src/problem_3216_lexicographically_smallest_string_after_a_swap/mod.rs

@@ -0,0 +1,18 @@
+pub mod greedy;
+
+pub trait Solution {
+    fn get_smallest_string(s: String) -> String;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    pub fn run<S: Solution>() {
+        let test_cases = [("45320", "43520"), ("001", "001")];
+
+        for (s, expected) in test_cases {
+            assert_eq!(S::get_smallest_string(s.to_string()), expected);
+        }
+    }
+}