如何避免我的错误排列算法：堆出内存

Question

Today I try to solve a problem on codewars ，it requires me give the permutations of a given string.

Firstly,I try to use a recursion function looks like:

function permutate(str) {

    var result = [];
    if (str.length == 1) {
        return [str]
    } else {

        var preResult = permutate(str.slice(1));
        for (var j = 0; j < preResult.length; j++) {
            for (var k = 0; k < preResult[j].length + 1; k++) {
                var temp = preResult[j].slice(0, k) + str[0] + preResult[j].slice(k);
                result.push(temp);
            }
        }
        return result;

    }
}

After I click the attemp button,the OJ tells me there is an error caused by heap out memory.Because my function called with a long string:"abcdefghijkl".

Secondly,I rewrite my function by using loop.just like:

function perm(str) {
    let result = [],tempArr = [];
    let subStr = str;
    while (subStr.length !== 0) {
        if (result.length === 0) {
            result.push(str[0]);
        } else {
            for (let i = 0; i < result.length; i++) {
                let item = result[i];
                let itemLen = item.length;
                for (let j = 0; j < itemLen+1; j++) {

                    let temp = item.slice(0, j) + subStr[0] + item.slice(j);
                    tempArr.push(temp);
                }
            }
            result = tempArr;
            tempArr = [];
        }
        subStr = subStr.slice(1);
    }
    return result;
}

It works when the given string is short.But still cause Error.

So,I want to know why cause this error and if there is a permutation algorithm can run in Node(v6.11.0) without memory error?

I searched a lot and tried many methods,but nothing works.So I ask my first question on stackoverflow,hoping you can give me some help.Thanks!

Answer 1

尝试使用模块https://github.com/miguelmota/permutations ，甚至尝试使用模块中的代码

Answer 2

除了可以尝试的先前答案外，您还可以尝试增加进程的最大内存限制大小，例如，使用node --max-old-space-size=8192 （以字节为单位），则节点进程将以扩展的8GB运行内存限制。