20 Valid Parentheses

Valid Parentheses

Given a string s containing just the characters ‘(‘, ‘)’, ‘{‘, ‘}’, ‘[’ and ‘]’, determine if the input string is valid.

An input string is valid if:

Open brackets must be closed by the same type of brackets.
Open brackets must be closed in the correct order.
Every close bracket has a corresponding open bracket of the same type.

 

Example 1:

Input: s = “()”

Output: true

Example 2:

Input: s = “()[]{}”

Output: true

Example 3:

Input: s = “(]”

Output: false

Example 4:

Input: s = “([])”

Output: true

 

Constraints:

1 <= s.length <= 104
s consists of parentheses only '()[]{}'.

/**
 * @param {string} s
 * @return {boolean}
 */


let isValid = (testString) => {

    let paran = []
    for (let i = 0 ; i < testString.length; i ++) {

        if (paran.length > 0 ) {
            let current = paran[paran.length - 1]
            if ( (current == '(' && testString[i] == ')' ) || (current == '[' && testString[i] == ']' ) || (current == '{' && testString[i] == '}' ) ){
                paran.pop()
            } else {
                 paran.push(testString[i])
            }   
        } else {
             paran.push(testString[i])
        }
    }

    return paran.length == 0
}