leetCode 22.Generate Parentheses

Problem

Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.

Example 1:

Input: n = 3
Output: ['((()))', '(()())', '(())()', '()(())', '()()()']

Example 2:

Input: n = 1
Output: ['()']

Constraints:

1 <= n <= 8

Approach

"(" , ")" called "open" and "close" each other. I need 3 open, 3close. open must be first. close can not be first. always behind open. so that means 1 open , 0 close, or 1 open, 1close -> open > close

Solution

var generateParenthesis = function (n) {
  const res = []
  backtracking(0, 0, '')
  return res

  function backtracking(open, close, cur) {
    if (close > open || open > n) return

    if (open == n && close == n) {
      res.push(cur)
      return
    }
    backtracking(open + 1, close, cur + '(')
    backtracking(open, close + 1, cur + ')')
  }
}