JavaScript中的自定义数组排序

Question

I have a task. Need to sort array of strings (cities) in following way:

• First city from array is randomly chosen.
• Next city must begins with last letter of previous city.
• If there is not such city, take random city again.

The question is: what type of loop should i use and how to implement sorting? Should i use Array.sort() method, and how i could transform original array of cities to new array dynamically. Which methods of Array.prototype should i use?

let cities = [ "New York", "Tokio", "Moscow", "London", "Los Angeles", "Paris", "Berlin", "Madrid", "Kiev", "Oslo", "Barcelona", "Washington", "Ankara", "Rome", "Prague", "Amsterdam", "Minsk"];

function getRandomCity(arr) {
    return arr[Math.floor(Math.random()*arr.length)];
}

function sort(arr) {
    let unsortedArray = [...arr]; 
    let sortedArray = [];
}

Answer 1

 let cities = ["New York", "Tokio", "Moscow", "London", "Los Angeles", "Paris", "Berlin", "Madrid", "Kiev", "Oslo", "Barcelona", "Washington", "Ankara", "Rome", "Prague", "Amsterdam", "Minsk"]; function getRandomCity(arr) { return Math.floor(Math.random() * arr.length); } function sort(arr) { let unsortedArray = [...arr]; let sortedArray = []; let char = "!"; // choose will take an index and then push the city at that index into the sortedArray and remove it from unsortedArray and store the last letter of that city in char (uppercased) function choose(index) { let city = unsortedArray.splice(index, 1)[0]; sortedArray.push(city); char = city.charAt(city.length - 1).toUpperCase(); } choose(getRandomCity(unsortedArray)); // first of all, choose a random city while (unsortedArray.length) { // while there still cities let index, test = unsortedArray.some(function(c, i) { // check if there is a city that begin with char index = i; // store the index in the process return c.charAt(0) === char; }); if(test) // if we found a city choose(index); // choose it else // if not choose(getRandomCity(unsortedArray)); // choose a random one } return sortedArray; } console.log(sort(cities)); 

Answer 2

You can use Array.prototype.slice() , Array.prototype.splice() , recursion to return random element from array, or element having first letter, case insensitive, same as previous element

 let cities = [ "New York", "Tokio", "Moscow", "London" , "Los Angeles", "Paris", "Berlin", "Madrid" , "Kiev", "Oslo", "Barcelona", "Washington" , "Ankara", "Rome", "Prague", "Amsterdam", "Minsk"]; let copyCities = cities.slice(0); function getRandomCity(copy, len, res = []) { let curr, next; if (res.length > 0) { next = copy.filter(function(city) { var prev = res[res.length -1].slice(-1); return new RegExp(city[0], "i").test(prev) }); if (next.length) next = copy.splice(copy.indexOf(next.shift()), 1); } if (copy.length === len || !next.length) { res.push(copy.splice(Math.floor(Math.random()*copy.length), 1)[0]); } else { res.push(next[0]); } if (res.length < len) { return getRandomCity(copy, len, res) } else { return res } } var _cities = getRandomCity(copyCities, cities.length); console.log(_cities);