1.说明：
题目要求找出n个括号所能组成的所有合法括号序列，所谓合法括号序列，指的是从左到右遍历序列，任意位置都满足，左括号的个数大于等于右括号的个数。
2.代码：
/*** @param {number} n* @return {string[]}*/
var generateParenthesis = function(n) {var stack = [];var result = [];var curLeft = 0;var curRight = 0;function getEnd(n) {var result = ''for (var i = 0; i < n; i++) {result += '()';}return result;}var end = getEnd(n);function reachEnd() {return stack.join('') == end;}function init() {for (var i = 0; i < n; i++) {stack.push('(')}for (var i = 0; i < n; i++) {stack.push(')')}result.push(stack.join(''));}init();while (!reachEnd()) {// 出栈while (true) {var ele = stack.pop();if (ele == '(') {curLeft++if (curLeft < curRight) {break;}}else {curRight++}}// 入栈while (curRight) {stack.push(')');curRight--;while (curLeft) {stack.push('(')curLeft--}while (curRight) {stack.push(')')curRight--}}result.push(stack.join(''))}return result
};