您好，老师。以下是我根据您的思路，自己写的代码。执行过程中超时了，但是不知道该如何优化代码，麻烦老师指点一二。

var findSubstring = function(s, words) {
    if (!s || !words.length) {
        return []
    }
    let children = []; // 存放所有子单词串联组成的单词
    let findChildren = (words, arr) => {
        if (!words.length) {
            children.push(arr.join(''))
            return
        }
        for (let i=0, length=words.length; i<length; i++) {
            let current = words.splice(i, 1)
            arr.push(current)
            findChildren(words, arr)
            arr.pop()
            words.splice(i, 0, current)
        }
    }
    findChildren(words, [])
    let result = [], index = -1;
    children.forEach(item => {
        index = s.indexOf(item);
        while (index >= 0) {
            result.push(index)
            index = s.indexOf(item, index+1)
        }
    })
    result = [...new Set(result)]
    return result;
};

// 输入的值
"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"
[“dhvf”,“sind”,“ffsl”,“yekr”,“zwzq”,“kpeo”,“cila”,“tfty”,“modg”,“ztjg”,“ybty”,“heqg”,“cpwo”,“gdcj”,“lnle”,“sefg”,“vimw”,“bxcb”]