五种方法实现全排列之方法四

<script>
//递推+插入
let pailie4=()=>
{
let arr=[1,2,3];
let res1=[[arr[0]]];
for(let e of arr.slice(1))
{
let res2=[];
for(let r of res1)
{
for(let i=0;i<=r.length;i++)
{
res2.push(r.slice(0,i).concat([e],r.slice(i)));
}
}
res1=res2;
}
for(let r of res1)
{
document.write(`${r}<br />`);
}
document.write(`total4=${res1.length}<br /><br />`);
};
pailie4();
</script>