var permutation = function(s) {
    const trace = [];
    const res = [];
    for (let i = 0; i < s.length;i++) {
        trace[i] = false;
    }

    function dfs(str) {
        if (str.length === s.length) {
            res.push(str);
            return;
        }
        for (let i = 0;i < s.length;i++) {
            if (trace[i] === true) continue;
            trace[i] = true;
            dfs(str + s[i]);
            trace[i] = false;
        } 
    }
    dfs('');
    return [...new Set(res)];
};