function solution(arrs){
let cats = new Map();
let ret = [];
let indx = 0;
arrs.forEach(arr=>{
arr.category.forEach(cat=>{
if(cats.get(cat)>=0){
let ind = cats.get(cat);
ret[ind].children.push({name:arr.name})
}
else{
let q = {name:cat, children:[]}
q.children.push({name: arr.name});
cats.set(cat,indx++);
ret.push(q);
}
})
})
return ret;
}
