Merge pull request #341 from soapyigu/Array

Add a solution to Minimum Remove to Make Valid Parentheses

Author: soapyigu

Array/MinimumRemoveMakeValidParentheses.swift

@@ -0,0 +1,47 @@
+/**
+ * Question Link: https://leetcode.com/problems/minimum-remove-to-make-valid-parentheses/
+ * Primary idea: Count the number of left brackets and append to result accordingly. Remove unnecessary left brackets from most right.
+ * Time Complexity: O(n), Space Complexity: O(1)
+ */
+
+class MinimumRemoveMakeValidParentheses {
+    func minRemoveToMakeValid(_ s: String) -> String {
+        var leftCount = 0, res = Array("")
+        
+        for char in s {
+            if char == "(" {
+                leftCount += 1
+                res.append(char)
+            } else if char == ")" {
+                if leftCount == 0 {
+                    continue
+                } else {
+                    leftCount -= 1
+                    res.append(char)
+                }
+            } else {
+                res.append(char)
+            }
+        }
+        
+        // remove unnecessary left bracket
+        if leftCount > 0 {
+            var i = res.count - 1
+
+            while i >= 0 {
+                if res[i] == "(" {
+                    res.remove(at: i)
+                    leftCount -= 1
+
+                    if leftCount == 0 {
+                        break
+                    }
+                }
+
+                i -= 1
+            }
+        }
+        
+        return String(res)
+    }
+}