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Zybooks?

Oct 29, 2020LeifMessinger
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React Short Circuit Evaluation

Feb 3, 2021C S

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import React, { useState } from 'react' import Welcome from '../components/Welcome' function About() { const [showWelcome, setShowWelcome] = useState(false) return ( <div> {showWelcome ? <Welcome /> : null} </div> <div> {showWelcome && <Welcome /> } </div> ) } export default App

copy to clipboard

Nov 19, 2022CodeCatch

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const copyToClipboard = str => {
const el = document.createElement('textarea');
el.value = str;
el.setAttribute('readonly', '');
el.style.position = 'absolute';
el.style.left = '-9999px';
document.body.appendChild(el);
const selected =
document.getSelection().rangeCount > 0
? document.getSelection().getRangeAt(0)
: false;
el.select();
document.execCommand('copy');
document.body.removeChild(el);
if (selected) {
document.getSelection().removeAllRanges();
document.getSelection().addRange(selected);
}
};
copyToClipboard('Lorem ipsum'); // 'Lorem ipsum' copied to clipboard.

doubly linked list

Nov 19, 2022CodeCatch

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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; // 5
list.head.value; // 3
list.head.next.value; // 2
list.tail.value; // 4
list.tail.previous.value; // 5
[...list.map(e => e.value)]; // [3, 2, 1, 5, 4]
list.removeAt(1); // 2
list.getAt(1).value; // 1
list.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

euclidean distance

Nov 19, 2022CodeCatch

0 likes • 3 views

const euclideanDistance = (a, b) =>
Math.hypot(...Object.keys(a).map(k => b[k] - a[k]));
euclideanDistance([1, 1], [2, 3]); // ~2.2361
euclideanDistance([1, 1, 1], [2, 3, 2]); // ~2.4495

QM Helper

Mar 22, 2022LeifMessinger

0 likes • 1 view

//QM Helper by Leif Messinger
//Groups numbers by number of bits and shows their binary representations.
//To be used on x.com
const minterms = prompt("Enter your minterms separated by commas").split(",").map(x => parseInt(x.trim()));
const maxNumBits = minterms.reduce(function(a, b) {
return Math.max(a, Math.log2(b));
});
const bitGroups = [];
for(let i = 0; i < maxNumBits; ++i){
bitGroups.push([]);
}
for(const minterm of minterms){
let outputString = (minterm+" ");
//Count the bits
let count = 0;
for (var i = maxNumBits; i >= 0; --i) {
if((minterm >> i) & 1){
++count;
outputString += "1";
}else{
outputString += "0";
}
}
bitGroups[count].push(outputString);
}
document.body.textContent = "";
document.body.style.setProperty("white-space", "pre");
for(const group of bitGroups){
for(const outputString of group){
document.body.textContent += outputString + "\r\n";
}
}

quick sort

Nov 19, 2022CodeCatch

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const quickSort = arr => {
const a = [...arr];
if (a.length < 2) return a;
const pivotIndex = Math.floor(arr.length / 2);
const pivot = a[pivotIndex];
const [lo, hi] = a.reduce(
(acc, val, i) => {
if (val < pivot || (val === pivot && i != pivotIndex)) {
acc[0].push(val);
} else if (val > pivot) {
acc[1].push(val);
}
return acc;
},
[[], []]
);
return [...quickSort(lo), pivot, ...quickSort(hi)];
};
quickSort([1, 6, 1, 5, 3, 2, 1, 4]); // [1, 1, 1, 2, 3, 4, 5, 6]