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// first, we create a stack class Node { constructor(newData, newNext) { this.next = newNext; this.data = newData; } delete = () => { console.log(`Deleting ${this.data} `); this.next = null; delete this.next; this.data = null; delete this.data; } print = () => { console.log(this.data); } } class LinkedStack { constructor() { var head = null; this.push = (data) => { let tmp = head; while (tmp != null) { let d = tmp.data; if (d.key === data.key) { console.log(`${data.key} already exists, just overwrite value to ${data.value}`); d.value = data.value return data; } tmp = tmp.next; } // no key found we just padd it on head = new Node(data, head); } this.pop = () => { let tmp = head; head = head.next; tmp.delete(); } this.remove = key => { let tmp = head; let trailer = null; while (tmp != null) { let data = tmp.data; if (data.key === key) { if (head === tmp) { head = head.next; } else { trailer.next = tmp.next; tmp.next = null; } return tmp; } else { trailer = tmp; tmp = tmp.next; } } } this.print = () => { console.log('---- printing ------'); if (head == null) { console.log('empty stack'); return; } for (let tmp = head; tmp != null; tmp = tmp.next) { tmp.print(); } } this.getValueFromKey = key => { for (let tmp = head; tmp != null; tmp = tmp.next) { if (tmp.data.key === key) { return tmp.data; } } return null; } this.length = () => { let cur = 0; for (let tmp = head; tmp != null; tmp = tmp.next) { cur++; } console.log(`Length of stac is ${cur}`); return cur; } this.clear = () => { let tmp = head; while (tmp != null) { let eraser = tmp; tmp = tmp.next; eraser.delete(); } head = null; } } // constructor // prototype functions } /* let a = new LinkedStack(); a.push(new KVPair(8, 'dexter')); a.push(new KVPair(28, 'david')); a.push(new KVPair(68, 'ricky')); let r = a.remove(68); console.log(r.data); let r1 = a.remove(8); console.log(r1.data); let r2 = a.remove(28); console.log(r2.data); a.print(); */ // HashTable // put // get // remove // { int, string } // collision --> chaining function KVPair( newKey, newValue) { this.key = (typeof newKey === 'number') ? newKey : -1; this.value = (typeof newValue === 'string') ? newValue : ''; } class MyHash { constructor(tableLength) { let hashTable = new Array(tableLength); this.put = kvPair => { if (kvPair.key !== -1) { let hash = kvPair.key % tableLength; console.log('hash is: ', hash); let n = hashTable[hash]; console.log(n); if (!n) { hashTable[hash] = new LinkedStack(); hashTable[hash].push(kvPair); } else { // don't push yet // take care of same keys n.push(kvPair); } } } // key this.get = key => { let hash = key % tableLength; let stack = hashTable[hash]; if (!stack) return null; let result = stack.getValueFromKey(key); return result ? result.value : null } // key this.remove = key => { let hash = key % tableLength; let stack = hashTable[hash]; if (!stack) return null; let result = stack.remove(key); return result ? result.data : null; } // display each linked list this.showTable = () => { for (let i =0; i < tableLength; i++) { let ht = hashTable[i]; if (ht) { console.log(`printing stack at index ${i}`); ht.print(); } } } } } let h = new MyHash(20); // put h.put(new KVPair(8, 'ricky')); h.put(new KVPair(2, 'david')); h.put(new KVPair(28, 'dexter')); h.put(new KVPair(68, 'neo')); h.put(new KVPair(68, 'NeoGeo')); h.showTable(); console.log(`......................Now using Map`); let s = Symbol('dexter'); let m = new Map(); m.set('ricky', { phone: '123456', age: 40 }); m.set(s, { phone: '6543321', age: 30 }); m.set(6680, { description: 'rickys bday' }); console.log(m.has('ricky')); console.log(m.has(s)); console.log(m.get('ricky')); console.log(m.size); for (let item of m) { console.log(item); }; /* console.log('-------- problem #1 MOST FREQUENT -----------'); let input = [1,2,2,3,3,3,4]; let hashTable = new Map(); for (let i = 0; i < input.length; i++) { let item = input[i]; if (hashTable.has(item)) { console.log(`${item} exists`); let count = hashTable.get(item); hashTable.set(item, ++count); } else { console.log(`${item} does not exist yet, let's add it and set value to 0`); hashTable.set(item, 1); } } let largestValue = 0; let answer = 0; for (let [key, value] of hashTable) { if (value > largestValue) { largestValue = value; answer = key; } console.log(`${key}, ${value}`); } console.log(answer); */ console.log('-------- problem #2 Pairs with Diff of 2-----------'); let input = [1,7,5,9,2,12,3]; let K = 2; let count = 0; for (let i = 0; i < input.length; i++) { for (let j = i; j < input.length; j++) { let value = Math.abs(input[j]-input[i]); if (value === K) { count++; console.log(`diff is ${value} at indexes ${i}, ${j}`); } } } console.log(count); // all operations are O(1) // Hash function // collision handling // - chaining // - probing (linear, quadratic, double hashing) |