1963. Minimum Number of Swaps to Make the String Balanced: AC

Author: tan-wei

Diff for: src/solution/mod.rs

@@ -1480,3 +1480,4 @@ mod s1959_minimum_total_space_wasted_with_k_resizing_operations;
 mod s1960_maximum_product_of_the_length_of_two_palindromic_substrings;
 mod s1961_check_if_string_is_a_prefix_of_array;
 mod s1962_remove_stones_to_minimize_the_total;
+mod s1963_minimum_number_of_swaps_to_make_the_string_balanced;

Diff for: src/solution/s1963_minimum_number_of_swaps_to_make_the_string_balanced.rs

@@ -0,0 +1,99 @@
+/**
+ * [1963] Minimum Number of Swaps to Make the String Balanced
+ *
+ * You are given a 0-indexed string s of even length n. The string consists of exactly n / 2 opening brackets '[' and n / 2 closing brackets ']'.
+ * A string is called balanced if and only if:
+ *
+ * 	It is the empty string, or
+ * 	It can be written as AB, where both A and B are balanced strings, or
+ * 	It can be written as [C], where C is a balanced string.
+ *
+ * You may swap the brackets at any two indices any number of times.
+ * Return the minimum number of swaps to make s balanced.
+ *  
+ * Example 1:
+ *
+ * Input: s = "][]["
+ * Output: 1
+ * Explanation: You can make the string balanced by swapping index 0 with index 3.
+ * The resulting string is "[[]]".
+ *
+ * Example 2:
+ *
+ * Input: s = "]]][[["
+ * Output: 2
+ * Explanation: You can do the following to make the string balanced:
+ * - Swap index 0 with index 4. s = "[]][][".
+ * - Swap index 1 with index 5. s = "[[][]]".
+ * The resulting string is "[[][]]".
+ *
+ * Example 3:
+ *
+ * Input: s = "[]"
+ * Output: 0
+ * Explanation: The string is already balanced.
+ *
+ *  
+ * Constraints:
+ *
+ * 	n == s.length
+ * 	2 <= n <= 10^6
+ * 	n is even.
+ * 	s[i] is either '[' or ']'.
+ * 	The number of opening brackets '[' equals n / 2, and the number of closing brackets ']' equals n / 2.
+ *
+ */
+pub struct Solution {}
+
+// problem: https://leetcode.com/problems/minimum-number-of-swaps-to-make-the-string-balanced/
+// discuss: https://leetcode.com/problems/minimum-number-of-swaps-to-make-the-string-balanced/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+impl Solution {
+    pub fn min_swaps(s: String) -> i32 {
+        s.chars().fold(1, |acc, c| {
+            if c == '[' {
+                acc + 1
+            } else if c == ']' && acc > 1 {
+                acc - 1
+            } else {
+                acc
+            }
+        }) / 2
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_1963_example_1() {
+        let s = "][][".to_string();
+
+        let result = 1;
+
+        assert_eq!(Solution::min_swaps(s), result);
+    }
+
+    #[test]
+    fn test_1963_example_2() {
+        let s = "]]][[[".to_string();
+
+        let result = 2;
+
+        assert_eq!(Solution::min_swaps(s), result);
+    }
+
+    #[test]
+    fn test_1963_example_3() {
+        let s = "[]".to_string();
+
+        let result = 0;
+
+        assert_eq!(Solution::min_swaps(s), result);
+    }
+}