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Commit 7e17577

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Merge pull request #64 from amejiarosario/improvements
Improvements
2 parents 9874647 + a93ac1b commit 7e17577

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17 files changed

+480
-14
lines changed

17 files changed

+480
-14
lines changed
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// brute force: O(nd) | O(1)
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function rotLeft(a, d) {
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for (let i = 0; i < d; i++) { // O(d)
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a.push(a.shift()); // O(n), shift O(n)
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}
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return a;
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}
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module.exports = rotLeft;
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// modulus for rotations: O(n^2) | O(1)
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function rotLeft(a, d) {
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const len = a.length;
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const rot = d % len;
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for (let i = 0; i < rot; i++) { // O(n^2)
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a.push(a.shift()); // O(n)
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}
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return a;
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}
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module.exports = rotLeft;
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// additional space: O(n) | O(n)
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function rotLeft(a, d) {
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const len = a.length;
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const rot = d % len;
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const b = [];
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for (let i = 0; i < len; i++) { // O(n)
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b[i] = a[(rot + i) % len]; // O(1)
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}
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return b;
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}
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module.exports = rotLeft;
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/*eslint-disable */
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// npx jest benchmarks/two-sum-implementations/two-sum.spec.js --watch --collectCoverage
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const implementations = [
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{ name: 1, fn: require('./01-array-rotation') },
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{ name: '1a', fn: require('./01a-array-rotation') },
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{ name: 2, fn: require('./02-array-rotation') },
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];
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implementations.forEach(({name, fn}) => {
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describe(`Two Sum: ${name}`, () => {
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it('should work on worst case', () => {
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const rots = 1000;
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const array = [1, 2, 3];
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expect(fn(array, rots)).toEqual([2,3,1]);
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});
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});
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});
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// Brute force: O(n^2) | O(1)
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function twoSum(nums, target) {
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for (let i = 0; i < nums.length - 1; i++) { // O(n^2)
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const diff = target - nums[i];
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const offset = i + 1;
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const idx = nums.slice(offset).findIndex((n) => n === diff); // O(n)
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const j = offset + idx;
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if (idx > -1) return [i, j];
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}
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return [];
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}
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module.exports = twoSum;

‎benchmarks/two-sum-implementations/02-two-sum.js

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// With a HashMap: O(n) | O(n)
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// [map w/dups handling] → O(n^2) | O(n)
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function twoSum(nums, target) {
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const map = nums.reduce((m, v, i) => { // O(n)
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const ids = m.get(v) || [];
@@ -8,8 +8,9 @@ function twoSum(nums, target) {
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for (let i = 0; i < nums.length; i++) { // O(n)
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const diff = target - nums[i];
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if (map.has(diff) && i !== map.get(diff)) {
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return [i, map.get(diff)];
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if (map.has(diff)) {
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const id = map.get(diff).find((j) => j > i);
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if (id > -1) return [i, id];
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}
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}
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// [map w/dups handling] → O(n^2) | O(n)
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function twoSum(nums, target) {
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const map = mapify(nums);
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for (let i = 0; i < nums.length; i++) { // O(n)
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const diff = target - nums[i];
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if (map.has(diff)) {
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const id = map.get(diff).find((j) => j > i);
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if (id > -1) return [i, id];
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}
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}
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return [];
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}
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function mapify(nums) {
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return nums.reduce((m, v, i) => { // O(n)
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const ids = m.get(v) || [];
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ids.push(i);
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return m.set(v, ids);
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}, new Map());
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}
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module.exports = twoSum;
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// sort + two pointers: O(n log n) | O(1)
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function twoSum(nums, target) {
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nums.sort((a, b) => a - b);
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let lo = 0;
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let hi = nums.length - 1;
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while (lo < hi) {
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const sum = nums[lo] + nums[hi];
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if (sum === target) {
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return [lo, hi];
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}
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if (sum > target) {
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hi--;
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} else {
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lo++;
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}
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}
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return [];
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}
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module.exports = twoSum;
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/*eslint-disable */
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// npx jest benchmarks/two-sum-implementations/two-sum.spec.js --watch --collectCoverage
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const implementations = [
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{ name: 1, fn: require('./01-two-sum') },
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{ name: '1a', fn: require('./01a-two-sum') },
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{ name: 2, fn: require('./02-two-sum') },
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{ name: '2a', fn: require('./02a-two-sum') },
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{ name: 3, fn: require('./03-two-sum') },
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{ name: 4, fn: require('./04-two-sum') },
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];
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implementations.forEach(({name, fn}) => {
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describe(`Two Sum: ${name}`, () => {
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xit('should work', () => {
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expect(fn([1, 2, 3].concat(Array(1e2 - 3).fill(7)), 4)).toEqual([0, 2]);
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});
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it('should work on worst case', () => {
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const size = 100;
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expect(fn([...Array(size).fill(2), 3, 3 * size * 10], 3 * size * 10 + 3)).toEqual([size, size + 1]);
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});
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});
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});
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const checkIfPrerequisite = function (n, prerequisites, queries) {
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const graph = new Map();
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Array(n).fill(0).forEach((v, i) => graph.set(i, {
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children: [],
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// connected: new Set(),
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}));
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prerequisites.forEach(([u, v]) => {
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graph.get(u).children.push(v);
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// graph.get(u).connected.add(v);
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});
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return queries.map(([u, v]) => isConnected(graph, u, v, new Set(), u));
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};
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function isConnected(graph, u, v, path = new Set(), p) {
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// console.log({u, v, path}, graph)
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// if (graph.get(u).connected.has(v)) return true;
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// path.forEach(s => graph.get(p).connected.add(s));
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for (const child of graph.get(u).children) {
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if (child === v) return true;
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if (path.has(child)) continue;
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if (isConnected(graph, child, v, path.add(u), p)) return true;
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}
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return false;
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}
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module.exports = checkIfPrerequisite;

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