全排列 #20

var permute = function(nums) {
     let res = []
     let fn = (path) => {
         if(path.length === nums.length) {
             res.push(path)
             return
         }
         nums.forEach(item => {
             if (!path.includes(item)) {
                 fn(path.concat(item))
             }
             
         })
     }
     fn([])
     return res
};