LC 1963. Minimum Number of Swaps to Make the String Balanced (Rust)

Author: raul-sauco

README.md

@@ -636,6 +636,7 @@ to the solution in this repository.
 | [1942. The Number of the Smallest Unoccupied Chair][lc1942]                                   | 🟠 Medium  | [![rust](res/rs.png)][lc1942rs]                                                                       |
 | [1945. Sum of Digits of String After Convert][lc1945]                                         | 🟢 Easy    | [![rust](res/rs.png)][lc1945rs]                                                                       |
 | [1962. Remove Stones to Minimize the Total][lc1962]                                           | 🟠 Medium  | [![python](res/py.png)][lc1962py]                                                                     |
+| [1963. Minimum Number of Swaps to Make the String Balanced][lc1963]                           | 🟠 Medium  | [![rust](res/rs.png)][lc1963rs]                                                                       |
 | [1964. Find the Longest Valid Obstacle Course at Each Position][lc1964]                       | 🔴 Hard    | [![rust](res/rs.png)][lc1964rs]                                                                       |
 | [1970. Last Day Where You Can Still Cross][lc1970]                                            | 🔴 Hard    | [![rust](res/rs.png)][lc1970rs]                                                                       |
 | [1971. Find if Path Exists in Graph][lc1971]                                                  | 🟢 Easy    | [![python](res/py.png)][lc1971py]                                                                     |
@@ -2172,6 +2173,8 @@ to the solution in this repository.
 [lc1945rs]: leetcode/sum-of-digits-of-string-after-convert.rs
 [lc1962]: https://leetcode.com/problems/remove-stones-to-minimize-the-total/
 [lc1962py]: leetcode/remove-stones-to-minimize-the-total.py
+[lc1963]: https://leetcode.com/problems/minimum-number-of-swaps-to-make-the-string-balanced/
+[lc1963rs]: leetcode/minimum-number-of-swaps-to-make-the-string-balanced.rs
 [lc1964]: https://leetcode.com/problems/find-the-longest-valid-obstacle-course-at-each-position/
 [lc1964rs]: leetcode/find-the-longest-valid-obstacle-course-at-each-position.rs
 [lc1970]: https://leetcode.com/problems/last-day-where-you-can-still-cross/

leetcode/minimum-number-of-swaps-to-make-the-string-balanced.rs

@@ -0,0 +1,76 @@
+// 1963. Minimum Number of Swaps to Make the String Balanced
+// 🟠 Medium
+//
+// https://leetcode.com/problems/minimum-number-of-swaps-to-make-the-string-balanced/
+//
+// Tags: Two Pointers - String - Stack - Greedy
+
+struct Solution;
+impl Solution {
+    /// Iterate the string, when the number of closing brackets is greater
+    /// than the number of opening brackets, we swap one with the furthest right opening bracket in
+    /// the string. We can do that using and updating counts rather than actually updating the
+    /// input string.
+    ///
+    /// Time complexity: O(n) - We visit each character in the input and do constant time work for
+    /// each.
+    /// Space complexity: O(1)
+    ///
+    /// Runtime 8 ms Beats 76%
+    /// Memory 4.70 MB Beats 75%
+    pub fn min_swaps(s: String) -> i32 {
+        // Not needed but helps with early break.
+        let mut remaining_opening = s.len() / 2;
+        let mut swaps = 0;
+        let (mut opening, mut closing) = (0, 0);
+        for c in s.chars() {
+            match c {
+                '[' => {
+                    opening += 1;
+                    remaining_opening -= 1;
+                }
+                _ => closing += 1,
+            }
+            if closing > opening {
+                swaps += 1;
+                remaining_opening -= 1;
+                opening += 1;
+                closing -= 1;
+            }
+            if remaining_opening == 0 {
+                break;
+            }
+        }
+        swaps
+    }
+}
+
+// Tests.
+fn main() {
+    let tests = [("][][", 1), ("]]][[[", 2), ("[]", 0)];
+    println!("\n\x1b[92m» Running {} tests...\x1b[0m", tests.len());
+    let mut success = 0;
+    for (i, t) in tests.iter().enumerate() {
+        let res = Solution::min_swaps(t.0.to_string());
+        if res == t.1 {
+            success += 1;
+            println!("\x1b[92m✔\x1b[95m Test {} passed!\x1b[0m", i);
+        } else {
+            println!(
+                "\x1b[31mx\x1b[95m Test {} failed expected: {:?} but got {}!!\x1b[0m",
+                i, t.1, res
+            );
+        }
+    }
+    println!();
+    if success == tests.len() {
+        println!("\x1b[30;42m✔ All tests passed!\x1b[0m")
+    } else if success == 0 {
+        println!("\x1b[31mx \x1b[41;37mAll tests failed!\x1b[0m")
+    } else {
+        println!(
+            "\x1b[31mx\x1b[95m {} tests failed!\x1b[0m",
+            tests.len() - success
+        )
+    }
+}