题解 | #火车进站#

const rl = require("readline").createInterface({ input: process.stdin });
var iter = rl[Symbol.asyncIterator]();
const readline = async () => (await iter.next()).value;

void async function () {
    const n = parseInt(await readline());
    const list = (await readline()).split(" ").map(Number);
    const res = [];
    const dfs = (list,insert,out) =>{
        if(out.length === n) return res.push(out.join(" "));
        if(insert.length){
            out.push(insert.pop());
            dfs(list,insert,out);
            insert.push(out.pop());//还原
        }
        if(list.length){
            insert.push(list.shift());
            dfs(list,insert,out);
            list.unshift(insert.pop());//还原
        }
    }
    dfs(list,[],[]);
    console.log(res.sort().join("\n"));
}()