第一题：Series: 1 + 1/4 + 1/7 + 1/10 + 1/13 + 1/16 +...
SeriesSum(1) => 1 = "1.00"
SeriesSum(2) => 1 + 1/4 = "1.25"
SeriesSum(5) => 1 + 1/4 + 1/7 + 1/10 + 1/13 = "1.57"
Examples:
function SeriesSum(n) {
let sum = 0;
for (let i = 0 ,k= 0; i <n; i++,k=k+3) {
sum += 1 / (k+ 1)
}
return sum.toFixed(2);
}
function SeriesSum(n) {
for (var s = 0, i = 0; i < n; i++) {
s += 1 / (1 + i * 3)
}
return s.toFixed(2)
}
console.log(SeriesSum(-1));
console.log(SeriesSum(0));
console.log(SeriesSum(1));
console.log(SeriesSum(2));
console.log(SeriesSum(3));
test.html: 0.00
test.html: 0.00
test.html: 1.00
test.html: 1.25
test.html: 1.39
第二题：验证长度为4或6的数字
ATM machines allow 4 or 6 digit PIN codes and PIN codes cannot contain anything but exactly 4 digits or exactly 6 digits.
If the function is passed a valid PIN string, return true, else return false.
function validatePIN (pin) {
//return true or false
let reg = /^(\d{4}|\d{6})$/
//let reg = /^\d{4}$|^\d{6}$/
if(reg.test(pin)){
return true;
}
return false
}
//长度符合 且为数组
function validatePIN (pin) {
var pinlen = pin.length;
var isCorrectLength = (pinlen == 4 || pinlen == 6);
var hasOnlyNumbers = pin.match(/^\d+$/);
if(isCorrectLength && hasOnlyNumbers){
return true;
}
return false;
}
第三题 用js将字符串中的元音字母删除并返回新数组
"This website is for losers LOL!"
"Ths wbst s fr lsrs LL!"
function disemvowel(str) {
return str.replace(/[aeiou]/gi,'');
}
function disemvowel(str) {
return (str || "").replace(/[aeiou]/gi, "");
}
第四题：字符串首字母全部变成大写
代码1
String.prototype.toJadenCase = function () {
let str = this;
let arr = str.split(' ');
for(let i=0; i < arr.length; i++) {
arr[i] = arr[i].charAt(0).toUpperCase() +arr[i].slice(1);
}
return arr.join(' ');
};
代码2
String.prototype.toJadenCase = function () {
return this.split(" ").map(function(word){
return word.charAt(0).toUpperCase() + word.slice(1);
}).join(" ");
}
代码3
String.prototype.toJadenCase = function () {
return this.replace(/(^|\s)[a-z]/g, function(x){ return x.toUpperCase(); });
}
第五题：类似于斐波那契函数，但它将序列的前3个（而不是2个）数相加以生成下一个
[1，1，1，3，5，9，17，31，…]
代码1
function tribonacci(signature, n) {
let res = []
for(let i=0;i<n;i++){
if(i<3){
res.push(signature[i]);
}else{
res.push(res[i-3]+res[i-2]+res[i-1]);
}
}
return res;
}
console.log(tribonacci([1,1,1],10));
[1, 1, 1, 3, 5, 9, 17, 31, 57, 105]
代码2
function tribonacci(signature,n){
for (var i = 0; i < n-3; i++) { // iterate n times
signature.push(signature[i] + signature[i+1] + signature[i+2]); // add last 3 array items and push to trib
}
return signature.slice(0, n); //return trib - length of n
}
代码3 从后往前找3个数求和放到当前位置。
function tribonacci(signature,n) {
const result = signature.slice(0, n);
while (result.length < n) {
result[result.length] = result.slice(-3).reduce((p,c) => p + c, 0);
}
return result;
}
第六题：字符串合并去重复然后排序
代码1
function longest(s1, s2) {
let mode = 'abcdefghijklmnopqrstuvwxyz';
let res = []
for(let item of mode){
console.log(item);
if(s1.includes(item) || s2.includes(item)){
res.push(item);
}
}
return res.join('')
}
代码2
const longest = (s1, s2) => [...new Set(s1+s2)].sort().join('')
代码3
function longest(s1, s2) {
return Array.from(new Set(s1 + s2)).sort().join('');
}
第七期：字符串2个2个一组，不够加_
solution('abc') // should return ['ab', 'c_']
solution('abcdef') // should return ['ab', 'cd', 'ef']
代码1
function solution(str) {
let res = []
str.split('').map((item, index) => {
if ((index + 1) % 2 == 0 && index + 1 <= str.length) {
res.push(str.charAt(index - 1) + str.charAt(index))
}
});
if (str.length % 2 != 0) {
res.push(str.charAt(str.length - 1) + '_')
}
return res;
}
代码2
function solution(str) {
return (str.length % 2 ? str + '_' : str).match(/../g);
}
第八题：一个电影院售票员在没有本金的情况下,进行售票,如果能够用收到的钱进行找零,则交易成功,如果整个队伍都能交易成功,返回YES,否则,返回NO.根据介绍,创建一个判断该排队队伍能不能成功交易
代码1
function tickets(peopleInLine) {
var twentyFifth = [], fifty = [], hundred = [],flag='';
for(var j=0;j<peopleInLine.length;j++){
if(peopleInLine[j]!=25){
if(peopleInLine[j]==50){
if(twentyFifth.length>0){
twentyFifth.shift();
fifty.push(50);
flag= 'YES';
}else{
flag= 'NO';
break;
}
}
else if(peopleInLine[j]==100){
if(twentyFifth.length>0 && fifty.length>0){
twentyFifth.shift();
fifty.shift();
hundred.push(100);
flag = 'YES';
}
else if(twentyFifth.length>=3){
twentyFifth.splice(0,3);
hundred.push(100);
flag = 'YES';
} else{
flag= 'NO';
break;
}
}
}else{
twentyFifth.push(25);
flag = 'YES';
}
}
return flag;
}
代码2
function Clerk(name) {
this.name = name;
this.money = {
25 : 0,
50 : 0,
100: 0
};
this.sell = function(element, index, array) {
this.money[element]++;
switch (element) {
case 25:
return true;
case 50:
this.money[25]--;
break;
case 100:
this.money[50] ? this.money[50]-- : this.money[25] -= 2;
this.money[25]--;
break;
}
return this.money[25] >= 0;
};
}
function tickets(peopleInLine){
var vasya = new Clerk("Vasya");
return peopleInLine.every(vasya.sell.bind(vasya)) ? "YES" : "NO";
}
代码3
function tickets(peopleInLine){
let [c25,c50,c100] = [0,0,0];
for(let v of peopleInLine) {
if(v===25) c25++;
if(v===50) {c50++; c25--;}
if(v===100) {c25--; c50>0?c50--:c25-=2;}
if(c25<0||c50<0) return 'NO'
}
return 'YES'
}
第九题：组数取基数排序，偶数原来位置不动
代码1
function sortArray(array) {
// Return a sorted array.
let map = {}
if(array && array.length ==0 ){
return [];
}
let arr = array.filter((item,index) => {
if(item % 2!==0 || item ==1){
return true;
}
else{
map[index] = item;
}
}).sort((a,b)=>a-b);
console.log(arr)
for(let key in map){
arr.splice(key,0,map[key])
}
console.log(arr)
return arr;
}
代码2 找出基数放到一个数组，原数组基数从基数数组取第一个依次替换。
function sortArray(array) {
const odd = array.filter((x) => x % 2).sort((a,b) => a - b);
return array.map((x) => x % 2 ? odd.shift() : x);
}
第十题：您将得到一个数字，您需要以展开形式将其作为字符串返回
expandedForm(12); // Should return '10 + 2'
expandedForm(42); // Should return '40 + 2'
expandedForm(70304); // Should return '70000 + 300 + 4'
代码1
function expandedForm(num) {
// Your code here
let str = num.toString()
let res = [];
for(let i=0;i<str.length;i++){
let item = parseInt(str.charAt(i));
if(item !==0){
res.push(item*Math.pow(10,str.length-i-1));
}
}
return res.join(' + ')
}
代码2
const expandedForm = n => n.toString()
.split("")
.reverse()
.map( (a, i) => a * Math.pow(10, i))
.filter(a => a > 0)
.reverse()
.join(" + ");
代码3
function expandedForm(num) {
return String(num)
.split("")
.map((num, index, arr) => num + "0".repeat(arr.length - index -1 ))
.filter((num) => Number(num) != 0)
.join(" + ")
}
