Merge pull request #1276 from rutanshuj/patch-9

Update 20-Valid-Parentheses.js

Author: aakhtar3

javascript/20-Valid-Parentheses.js

@@ -1,10 +1,10 @@
 /**
- * https://leetcode.com/problems/valid-parentheses
  * Time O(N) | Space O(N)
+ * https://leetcode.com/problems/valid-parentheses/
  * @param {string} s
  * @return {boolean}
  */
- var isValid = function(s, stack = []) {
+ var isValid = (s, stack = []) => {
     for (const bracket of s.split('')) {/* Time O(N) */
         const isParenthesis = bracket === '(';
         if (isParenthesis) stack.push(')');  /* Space O(N) */
@@ -15,13 +15,40 @@
         const isSquareBracket = bracket === '[';
         if (isSquareBracket) stack.push(']');/* Space O(N) */
 
-        const isOpenBracket = isParenthesis || isCurlyBrace || isSquareBracket;
-        if (isOpenBracket) continue;
+        const isOpenPair = isParenthesis || isCurlyBrace || isSquareBracket;
+        if (isOpenPair) continue;
 
         const isEmpty = !stack.length;
         const isWrongPair = stack.pop() !== bracket;
         const isInvalid = isEmpty || isWrongPair;
         if (isInvalid) return false;
     }
-    return stack.length === 0;
+
+    return (stack.length === 0);
+};
+
+/**
+ * Time O(N) | Space O(N)
+ * https://leetcode.com/problems/valid-parentheses/
+ * @param {string} s
+ * @return {boolean}
+ */
+var isValid = (s, stack = []) => {
+    const map = {
+        '}': '{',
+        ']': '[',
+        ')': '(',
+    };
+    
+    for (const char of s) {/* Time O(N) */
+        const isBracket = (char in map)
+        if (!isBracket) { stack.push(char); continue; }/* Space O(N) */
+
+        const isEqual = (stack[stack.length - 1] === map[char])
+        if (isEqual) { stack.pop(); continue; }
+
+        return false;
+    }
+
+    return (stack.length === 0);
 };