implemented lcm and gcd algorithms

packages/web/src/lib/maths.test.ts

@@ -1,9 +1,36 @@
 import { describe, expect, test, } from "vitest";
+import { gcd, lcm } from "./maths";
 
 describe("maths", function() {
-    describe("gcd", function() {
-        test("should do something", function() {
-            expect(1).to.be.equal(1)
+    test("lcm", function() {
+        const tests = [
+            { inputs: [1], expected: 1 },
+            { inputs: [1, 2], expected: 2 },
+            { inputs: [2, 3], expected: 6 },
+            { inputs: [2, 4], expected: 4 },
+            { inputs: [2, 3, 4], expected: 12 },
+            { inputs: [1, 3, 5, 8], expected: 120 },
+        ]
+
+        tests.forEach((test, i) => {
+            expect(lcm(test.inputs)).to.equal(test.expected, `tests[${i}]: expected ${test.inputs} to have ${test.expected} as lcm`);
+        })
+    })
+
+    test("gcd", function() {
+        const tests = [
+            { inputs: [1], expected: 1 },
+            { inputs: [1, 2], expected: 1 },
+            { inputs: [2, 3], expected: 1 },
+            { inputs: [2, 4], expected: 2 },
+            { inputs: [2, 3, 4], expected: 1 },
+            { inputs: [3, 6, 18], expected: 3 },
+            { inputs: [12, 18], expected: 6 },
+        ]
+
+        tests.forEach((test, i) => {
+            expect(gcd(test.inputs)).to.equal(test.expected, `tests[${i}]: expected ${test.inputs} to have ${test.expected} as gcd`);
         })
+
     })
 })

packages/web/src/lib/maths.ts

@@ -1,13 +1,49 @@
 /***
 * Greatest Common Divisor
 */
-export function gcd(n: number): number {
-    return 0
+export function gcd(n: number[]): number {
+    if (n.length === 1) {
+        return n[0]
+    }
+
+    // NOTE: See Euclidean algorithm 
+    if (n.length === 2) {
+        let [a, b] = n
+        while (b !== 0) {
+            let t = b
+            b = a % b
+            a = t
+        }
+        return a
+    }
+
+    const stack = [...n]
+    while (stack.length >= 2) {
+        let a = stack.pop()!
+        let b = stack.pop()!
+        stack.push(gcd([a, b]))
+    }
+    return stack[0]
 }
 
 /**
 * Lowest Common Multiple
 */
-export function lcm(n: number): number {
-    return 0
+export function lcm(n: number[]): number {
+    if (n.length === 0) {
+        return 0
+    }
+
+    if (n.length <= 2) {
+        const product = n.reduce((p, curr) => p * curr, 1)
+        return product / gcd(n)
+    }
+
+    const stack = [...n]
+    while (stack.length >= 2) {
+        let a = stack.pop()!
+        let b = stack.pop()!
+        stack.push(lcm([a, b]))
+    }
+    return stack[0]
 }