LC 921. Minimum Add to Make Parentheses Valid (Rust)

Author: raul-sauco

README.md

@@ -416,6 +416,7 @@ to the solution in this repository.
 | [912. Sort an Array][lc912]                                                                   | 🟠 Medium  | [![python](res/py.png)][lc912py] [![rust](res/rs.png)][lc912rs]                                       |
 | [916. Word Subsets][lc916]                                                                    | 🟠 Medium  | [![python](res/py.png)][lc916py]                                                                      |
 | [918. Maximum Sum Circular Subarray][lc918]                                                   | 🟠 Medium  | [![python](res/py.png)][lc918py] [![rust](res/rs.png)][lc918rs]                                       |
+| [921. Minimum Add to Make Parentheses Valid][lc921]                                           | 🟠 Medium  | [![rust](res/rs.png)][lc921rs]                                                                        |
 | [926. Flip String to Monotone Increasing][lc926]                                              | 🟠 Medium  | [![python](res/py.png)][lc926py] [![rust](res/rs.png)][lc926rs]                                       |
 | [930. Binary Subarrays With Sum][lc930]                                                       | 🟠 Medium  | [![rust](res/rs.png)][lc930rs]                                                                        |
 | [931. Minimum Falling Path Sum][lc931]                                                        | 🟠 Medium  | [![python](res/py.png)][lc931py]                                                                      |
@@ -1674,6 +1675,8 @@ to the solution in this repository.
 [lc918]: https://leetcode.com/problems/maximum-sum-circular-subarray/
 [lc918py]: leetcode/maximum-sum-circular-subarray.py
 [lc918rs]: leetcode/maximum-sum-circular-subarray.rs
+[lc921]: https://leetcode.com/problems/minimum-add-to-make-parentheses-valid/
+[lc921rs]: leetcode/minimum-add-to-make-parentheses-valid.rs
 [lc926]: https://leetcode.com/problems/flip-string-to-monotone-increasing/
 [lc926py]: leetcode/flip-string-to-monotone-increasing.py
 [lc926rs]: leetcode/flip-string-to-monotone-increasing.rs

leetcode/minimum-add-to-make-parentheses-valid.rs

@@ -0,0 +1,61 @@
+// 921. Minimum Add to Make Parentheses Valid
+// 🟠 Medium
+//
+// https://leetcode.com/problems/minimum-add-to-make-parentheses-valid/
+//
+// Tags: String - Stack - Greedy
+
+struct Solution;
+impl Solution {
+    /// Iterate over the input keeping track of the number of open left parentheses we find, for
+    /// each unmatched or extra parentheses we will need to add a matching one.
+    ///
+    /// Time complexity: O(n)
+    /// Space complexity: O(1)
+    ///
+    /// Runtime 1 ms Beats 58%
+    /// Memory 2.18 MB Beats 23%
+    pub fn min_add_to_make_valid(s: String) -> i32 {
+        let (mut left, mut right) = (0, 0);
+        for c in s.chars() {
+            if c == '(' {
+                right += 1;
+            } else if right > 0 {
+                right -= 1;
+            } else {
+                left += 1;
+            }
+        }
+        right + left
+    }
+}
+
+// Tests.
+fn main() {
+    let tests = [("())", 1), ("(((", 3)];
+    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_add_to_make_valid(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
+        )
+    }
+}