javascript - n对括号的所有有效组合

Question

我正在尝试编写一个 js 程序来打印 n 对括号的所有有效组合，例如:

(), (()()),(())。

你能告诉我这是否正确吗？

https://jsfiddle.net/e7mcp6xb/

module.exports = Parentheses = (function() {
  var _isParenthesesMatch = function(str) {
    var parentheses = str.length;
    var rightParentheses = '(';
    var leftParentheses = ')';
    var rightCount = 0;
    var leftCount = 0;

    for(i=0;i<=str.length;i++){
       if(rightParentheses == str.charAt(i))
       {
          rightCount++;
       }
       else if(leftParentheses == str.charAt(i))
       {
          leftCount++;
       }
    }

    if(rightCount == leftCount){
      return true;
    }
    else(rightCount != leftCount){
      return false;
    }

  }
  
}());

Answer 1

检查错误，但您可以轻松修复:在 for 循环的每一步中，左括号的数量不能小于右括号的数量:

if (rightCount < leftCount)
    return false;

整个函数应该是这样的:

function(str) {
    var rightParentheses = '(';
    var leftParentheses = ')';
    var rightCount = 0;
    var leftCount = 0;

    for (var i = 0; i <= str.length; i++) {
       if (rightParentheses == str.charAt(i))
          rightCount++;
       else if (leftParentheses == str.charAt(i))
          leftCount++;

       if (rightCount < leftCount)
          return false;
    }

    return rightCount == leftCount;
}

如果你想生成所有有效的字符串，你可以使用这个函数:

function nPair(n) {
    if (n == 0)
        return [""];

    var result = [];
    for (var i = 0; i < n; ++i) {

        var lefts = nPair(i);
        var rights = nPair(n - i - 1);

        for (var l = 0; l < lefts.length; ++l)
            for (var r = 0; r < rights.length; ++r)
                result.push("(" + lefts[l] + ")" + rights[r]);
    }

    return result;
}

// result of nPair(3):
// ["()()()", "()(())", "(())()", "(()())", "((()))"]