We iterate over the given string ss. When we encounter an open parenthesis, we expect it to be closed by a close parenthesis of the same type in subsequent traversals. Since the left parenthesis encountered later is closed first, we can place the left parenthesis at the top of the stack.
When we encounter a close parenthesis, we need to close an open parenthesis of the same type. At this point, we can pull out the left parentheses at the top of the stack and determine if they are of the same type. If they are not of the same type, or there are no open parentheses in the stack, then the string ss is invalid, returning \text{False}False. To quickly determine the type of parentheses, we can use a hash table to store each type of parentheses. The keys of the hash table are close parentheses and the values are open parentheses of the same type.
At the end of the loop, if there are no left parentheses in the stack, we close all the left parentheses in the string ss and return \text{True}True, otherwise return \text{False}False.
Note that the length of a valid string must be even, so if the length of the string is odd, we can return \text{False}False without further traversal.
Var isValid = function(s) {const len=s.length if(len%2===1){return false} const sMap=new Map( Right parenthesis matching directly [') ', '('], [']', '['], ['}', '{']]) const arr = [] for (let I = 0; i<len; I++) {if (sMap) from the (s) [I]) {/ / stack, advanced matching after the console. The log (sMap. Get [I]) (s) if (! arr.length||arr[arr.length-1]! ==sMap.get(s[i])){ return false }else{ arr.pop() } }else{ arr.push(s[i]) } } return ! arr.length }
