Add problem 1850: Minimum Adjacent Swaps to Reach the Kth Smallest Nu…

…mber

src/lib.rs

@@ -1380,6 +1380,7 @@ pub mod problem_1846_maximum_element_after_decreasing_and_rearranging;
 pub mod problem_1847_closest_room;
 pub mod problem_1848_minimum_distance_to_the_target_element;
 pub mod problem_1849_splitting_a_string_into_descending_consecutive_values;
+pub mod problem_1850_minimum_adjacent_swaps_to_reach_the_kth_smallest_number;
 pub mod problem_1851_minimum_interval_to_include_each_query;
 pub mod problem_1854_maximum_population_year;
 pub mod problem_1855_maximum_distance_between_a_pair_of_values;

src/problem_1850_minimum_adjacent_swaps_to_reach_the_kth_smallest_number/brute_force.rs

@@ -0,0 +1,59 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl Solution {
+    pub fn get_min_swaps(num: String, k: i32) -> i32 {
+        let mut num = num.into_bytes();
+        let mut target_num = num.clone();
+        let k = k as u32;
+        let mut result = 0;
+
+        for _ in 0..k {
+            let mut i = target_num.len();
+            let mut prev = 0;
+
+            for &x in target_num.iter().rev() {
+                i -= 1;
+
+                let found = x < prev;
+
+                prev = x;
+
+                if found {
+                    break;
+                }
+            }
+
+            let j = i + 1 + target_num[i + 2..].partition_point(|&x| x > prev);
+
+            target_num.swap(i, j);
+            target_num[i + 1..].reverse();
+        }
+
+        for (i, &target) in target_num.iter().enumerate() {
+            let j = num[i..].iter().position(|&c| c == target).unwrap();
+
+            result += j;
+            num[i..i + 1 + j].rotate_right(1);
+        }
+
+        result as _
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn get_min_swaps(num: String, k: i32) -> i32 {
+        Self::get_min_swaps(num, k)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}

src/problem_1850_minimum_adjacent_swaps_to_reach_the_kth_smallest_number/mod.rs

@@ -0,0 +1,18 @@
+pub mod brute_force;
+
+pub trait Solution {
+    fn get_min_swaps(num: String, k: i32) -> i32;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    pub fn run<S: Solution>() {
+        let test_cases = [(("5489355142", 4), 2), (("11112", 4), 4), (("00123", 1), 1)];
+
+        for ((num, k), expected) in test_cases {
+            assert_eq!(S::get_min_swaps(num.to_string(), k), expected);
+        }
+    }
+}