1. 深度搜索递归

let n = 3;
let usedNums = new Int32Array(10);//一个元素只能用一次 
let output = [];

//深度搜索
let dfs = x => {
    if (x > 0) output.push(x);
    if (output.length === n) console.log(output.join(' '));
    usedNums[x]++;//已使用标记
    for (let i = 1; i <= n; i++)
        if (!usedNums[i]) dfs(i);//递归
    usedNums[x]--;//回溯
    output.pop(x);
}


let buf = '';
process.stdin.on('readable', function () {
    let chunk = process.stdin.read();
    if (chunk) buf += chunk.toString();
});
let getInputNums = line => line.split(' ').filter(s => s !== '').map(x => parseInt(x));
let getInputStr = line => line.split(' ').filter(s => s !== '');
process.stdin.on('end', function () {
    buf.split('\n').forEach(function (line, lineIdx) {
        if (lineIdx === 0) {
            let a = getInputNums(line);
            n = a[0];
            dfs(0);
            //loop(n);
        }
    });
});

2. 深搜的非递归版本

let loop = n => {
    let usedNums = new Int32Array(10);//一个元素只能用一次 
    let stack = [0]; //存储已使用的节点
    //存储每一层即将使用的分支, 从1开始
    let deepUnused = new Array(n + 1).fill(1);

    while (stack.length > 0) {
        let deep = stack.length;
        let branch = deepUnused[deep];
        //先确定出口，当前分支枚举完，回溯
        if(deepUnused[deep] > n || stack.length > n){
            deepUnused[deep] = 1;
            usedNums[stack.pop()]--;
            continue;
        }
        while (branch <= n) { 
            if (!usedNums[branch]) { // 找到一条分支后，进入下一层
                usedNums[branch]++;
                stack.push(branch);
                deepUnused[deep] = ++branch;
                break;
            }
            deepUnused[deep] = ++branch;
        }
        //到达终点
        if(stack.length > n) console.log(stack.slice(1).join(' '));
    }
}