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const binomialCoefficient = (n, k) => {if (Number.isNaN(n) || Number.isNaN(k)) return NaN;if (k < 0 || k > n) return 0;if (k === 0 || k === n) return 1;if (k === 1 || k === n - 1) return n;if (n - k < k) k = n - k;let res = n;for (let j = 2; j <= k; j++) res *= (n - j + 1) / j;return Math.round(res);};binomialCoefficient(8, 2); // 28
class DoublyLinkedList {constructor() {this.nodes = [];}get size() {return this.nodes.length;}get head() {return this.size ? this.nodes[0] : null;}get tail() {return this.size ? this.nodes[this.size - 1] : null;}insertAt(index, value) {const previousNode = this.nodes[index - 1] || null;const nextNode = this.nodes[index] || null;const node = { value, next: nextNode, previous: previousNode };if (previousNode) previousNode.next = node;if (nextNode) nextNode.previous = node;this.nodes.splice(index, 0, node);}insertFirst(value) {this.insertAt(0, value);}insertLast(value) {this.insertAt(this.size, value);}getAt(index) {return this.nodes[index];}removeAt(index) {const previousNode = this.nodes[index - 1] || null;const nextNode = this.nodes[index + 1] || null;if (previousNode) previousNode.next = nextNode;if (nextNode) nextNode.previous = previousNode;return this.nodes.splice(index, 1);}clear() {this.nodes = [];}reverse() {this.nodes = this.nodes.reduce((acc, { value }) => {const nextNode = acc[0] || null;const node = { value, next: nextNode, previous: null };if (nextNode) nextNode.previous = node;return [node, ...acc];}, []);}*[Symbol.iterator]() {yield* this.nodes;}}const list = new DoublyLinkedList();list.insertFirst(1);list.insertFirst(2);list.insertFirst(3);list.insertLast(4);list.insertAt(3, 5);list.size; // 5list.head.value; // 3list.head.next.value; // 2list.tail.value; // 4list.tail.previous.value; // 5[...list.map(e => e.value)]; // [3, 2, 1, 5, 4]list.removeAt(1); // 2list.getAt(1).value; // 1list.head.next.value; // 1[...list.map(e => e.value)]; // [3, 1, 5, 4]list.reverse();[...list.map(e => e.value)]; // [4, 5, 1, 3]list.clear();list.size; // 0
console.log("xa")
const longestPalindrome = (s) => {if(s.length === 1) return sconst odd = longestOddPalindrome(s)const even = longestEvenPalindrome(s)if(odd.length >= even.length) return oddif(even.length > odd.length) return even};const longestOddPalindrome = (s) => {let longest = 0let longestSubStr = ""for(let i = 1; i < s.length; i++) {let currentLongest = 1let currentLongestSubStr = ""let left = i - 1let right = i + 1while(left >= 0 && right < s.length) {const leftLetter = s[left]const rightLetter = s[right]left--right++if(leftLetter === rightLetter) {currentLongest += 2currentLongestSubStr = s.slice(left+1, right)} else break}if(currentLongest > longest) {if(currentLongestSubStr) longestSubStr = currentLongestSubStrelse longestSubStr = s[i]longest = currentLongest}}return longestSubStr}const longestEvenPalindrome = (s) => {let longest = 0let longestSubStr = ""for(let i = 0; i < s.length - 1; i++) {if(s[i] !== s[i+1]) continue;let currentLongest = 2let currentLongestSubStr = ""let left = i - 1let right = i + 2while(left >= 0 && right < s.length) {const leftLetter = s[left]const rightLetter = s[right]left--right++if(leftLetter === rightLetter) {currentLongest += 2currentLongestSubStr = s.slice(left+1, right)} else break}if(currentLongest > longest) {if(currentLongestSubStr) longestSubStr = currentLongestSubStrelse longestSubStr = s[i] + s[i+1]longest = currentLongest}}return longestSubStr}console.log(longestPalindrome("babad"))
function Clock(props) {return (<div><h1>Hello, world!</h1><h2>It is {props.date.toLocaleTimeString()}.</h2></div>);}function tick() {ReactDOM.render(<Clock date={new Date()} />,document.getElementById('root'));}setInterval(tick, 1000);
const celsiusToFahrenheit = (celsius) => celsius * 9/5 + 32;const fahrenheitToCelsius = (fahrenheit) => (fahrenheit - 32) * 5/9;// ExamplescelsiusToFahrenheit(15); // 59celsiusToFahrenheit(0); // 32celsiusToFahrenheit(-20); // -4fahrenheitToCelsius(59); // 15fahrenheitToCelsius(32); // 0