LeetCode 22. Generate Parentheses (javascript)

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

Idea:

Backtracking

Solution:

/**
 * @param {number} n
 * @return {string[]}
 */
var generateParenthesis = function(n) {
    let ans = [];
    backtrack(ans, "", 0, 0, n);
    return ans;
}

function backtrack(ans, cur, open, close, max){
    // exit recursive condition
    if (cur.length === max * 2) {
        ans.push(cur.concat());
        return;
    }
    // possible solution
    if (open < max)
        backtrack(ans, cur + "(", open + 1, close, max);
    if (close < open)
        backtrack(ans, cur + ")", open, close + 1, max);
}