Update 20-Valid-Parentheses.js

aakhtar3 · web-flow · commit dc475b92a041 · 2022-10-16T23:27:52.000-04:00
diff --git a/javascript/20-Valid-Parentheses.js b/javascript/20-Valid-Parentheses.js
@@ -1,25 +1,54 @@
 /**
+ * Time O(N) | Space O(N)
+ * https://leetcode.com/problems/valid-parentheses/
  * @param {string} s
  * @return {boolean}
  */
-var isValid = function(s) {
-    let stack = [];
-    let map = {
+ var isValid = (s, stack = []) => {
+    for (const bracket of s.split('')) {/* Time O(N) */
+        const isParenthesis = bracket === '(';
+        if (isParenthesis) stack.push(')');  /* Space O(N) */
+
+        const isCurlyBrace = bracket === '{';
+        if (isCurlyBrace) stack.push('}');   /* Space O(N) */
+
+        const isSquareBracket = bracket === '[';
+        if (isSquareBracket) stack.push(']');/* Space O(N) */
+
+        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);
+};
+
+/**
+ * Time O(N) | Space O(N)
+ * https://leetcode.com/problems/valid-parentheses/
+ * @param {string} s
+ * @return {boolean}
+ */
+var isValid = (s, stack = []) => {
+    const map = {
         '}': '{',
         ']': '[',
-        ')':'(',
+        ')': '(',
     };
-    if(s.length < 2) return false;
-    for(let i=0; i<s.length; i++){
-        if(s[i] in map){
-            if(stack[stack.length-1] == map[s[i]]){
-                stack.pop();
-            } else{
-                return false;
-            }
-        } else {
-            stack.push(s[i]);
-        }
+    
+    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;
+
+    return (stack.length === 0);
 };
