House Party

function solve(input) {
   let list = [];

   for (let line of input) {
       let tokens = line.split(' ');
       let name = tokens[0];
       if (tokens.length===3) {
           let isIncluded = list.includes(name);
           if (isIncluded) {
               console.log(`${name} is already in the list!`);
           } else {
               list.push(name);
           }
       } else {
            let indexOfPerson = list.indexOf(name);
            if(indexOfPerson===-1){
                console.log(`${name} is not in the list!`);
            } else {
                list.splice(indexOfPerson, 1);
            }
       }
   }
   console.log(list.join('\n'));
}

//Write a function that keeps track of guests that are going to a house party.