Create ValidParentheses_p20.js

Add JS solution for - 20. Valid Parentheses

Author: tumanob

JsSolutions/ValidParentheses_p20.js

@@ -0,0 +1,34 @@
+/**
+ * https://leetcode.com/problems/valid-parentheses/
+ * 
+ * stack Data structure example
+ * https://initjs.org/data-structure-stack-in-javascript-714f45dbf889
+ * 
+ */
+
+/**
+ * @param {string} s
+ * @return {boolean}
+ */
+var isValid = function (s) {
+	if (s.length == 1) return false
+	if (s.length == 0) return true
+
+	let stack = []
+	let myMap = new Map()
+	myMap.set('(', ')')
+	myMap.set('{', '}')
+	myMap.set('[', ']')
+
+	for (char of s) { // complexity in O(N) as we go throught the string once
+		if (char === '(' || char === '{' || char === '[') {
+			stack.push(char) // in worst case it gives another O(N) in space and time "((((((..."
+		} else {
+			if (char !== myMap.get(stack[stack.length - 1])) 
+				return false
+			stack.pop()
+		}
+	}
+
+	return stack.length === 0
+};