Add problem 0670: Maximum Swap

src/lib.rs

@@ -375,6 +375,7 @@ pub mod problem_0650_2_keys_keyboard;
 pub mod problem_0653_two_sum_iv_input_is_a_bst;
 pub mod problem_0654_maximum_binary_tree;
 pub mod problem_0665_non_decreasing_array;
+pub mod problem_0670_maximum_swap;
 pub mod problem_0673_number_of_longest_increasing_subsequence;
 pub mod problem_0674_longest_continuous_increasing_subsequence;
 pub mod problem_0677_map_sum_pairs;

src/problem_0670_maximum_swap/iterative.rs

@@ -0,0 +1,43 @@
+pub struct Solution;
+
+use std::collections::HashMap;
+
+impl Solution {
+    pub fn maximum_swap(num: i32) -> i32 {
+        let mut nums = Vec::new();
+        let mut map = HashMap::new();
+        let mut num = num;
+        while num != 0 {
+            let digit = num % 10;
+            map.entry(digit).or_insert_with(|| nums.len());
+            nums.push(digit);
+            num /= 10;
+        }
+
+        let mut nums_sorted = nums.clone();
+        nums_sorted.sort_unstable();
+
+        for idx in (0..nums.len()).rev() {
+            if nums[idx] < nums_sorted[idx] {
+                nums.swap(idx, map[&nums_sorted[idx]]);
+                break;
+            }
+        }
+
+        nums.into_iter().rev().fold(0, |acc, x| acc * 10 + x)
+    }
+}
+
+impl super::Solution for Solution {
+    fn maximum_swap(num: i32) -> i32 {
+        Self::maximum_swap(num)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}

src/problem_0670_maximum_swap/mod.rs

@@ -0,0 +1,35 @@
+pub mod iterative;
+
+pub trait Solution {
+    fn maximum_swap(num: i32) -> i32;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    pub fn run<S: Solution>() {
+        let test_cases = [
+            (0, 0),
+            (1, 1),
+            (2, 2),
+            (3, 3),
+            (4, 4),
+            (5, 5),
+            (6, 6),
+            (7, 7),
+            (8, 8),
+            (9, 9),
+            (10, 10),
+            (11, 11),
+            (12, 21),
+            (13, 31),
+            (2736, 7236),
+            (9973, 9973),
+        ];
+
+        for (num, expected) in test_cases {
+            assert_eq!(S::maximum_swap(num), expected);
+        }
+    }
+}