<div class="input"><div>
<ul class="hide">
  <li class="heading"><a href="google.com/samsung">Телевизоры</a>   
     <ul>
       <li><a href="google.com/samsung" href="google.com/samsung">Samsung</a></li>
       <li><a href="google.com/samsung" href="google.com/samsung">Lenovo</a></li>
     </ul>
  </li>
  <li class="heading"><a href="google.com/samsung">Планшеты</a>   
     <ul>
       <li><a href="google.com/lenovo-03">Lenovo</a></li>
       <li><a href="google.com/samsung">Samsung</a></li>
       <li><a href="google.com/acer-43">Acer</a></li>
     </ul>
   </li>
  <li class="heading"><a>Ноутбуки</a>     
     <ul>
       <li><a href="google.com/lenovo-83">Lenovo</a></li>
       <li><a href="google.com/samsung-323">Samsung</a></li>
       <li><a href="google.com/acer-021">Acer</a></li>
     </ul>
  </li>
</ul>

.some-style {
    background-color: silver;
    border: 1px solid black;
}
.hide {
  display: none;
}

let heading = document.querySelectorAll(".heading");
let map = new Map();
for (let i = 0; i < heading.length; ++i) {
    let a = heading[i].querySelectorAll("a");
    let groupName = a[0].textContent.trim();
    for (let j = 1; j < a.length; ++j) {
        let companyName = a[j].textContent.trim();
        let href = a[j].href;
        let companyGroups = map.get(companyName);
        if (companyGroups) companyGroups.push({ groupName, href });
        else map.set(companyName, [{ groupName, href }]);
    }
}

let compare = (new Intl.Collator("ru")).compare;
let ul = document.createElement("ul");
ul.className = "some-style";
let companies = Array.from(map.keys()).sort(compare);
for (let companyName of companies) {
    let li = document.createElement("li");
    let a = document.createElement("a");
    a.textContent = companyName;
    li.append(a);
    
    let li_ul = document.createElement("ul");
    let companyGroups = map.get(companyName).sort(compare);
    for (let groupName of companyGroups) {
        let li = document.createElement("li");
        let a = document.createElement("a");
        a.textContent = groupName;
        li.append(a);
        li_ul.append(li);
    }
    li.append(li_ul);
    
    ul.append(li);
}

document.querySelector('.input').append(ul);