https://leetcode.cn/problems/fraction-addition-and-subtraction/

Author: masx200

README.md

@@ -904,6 +904,8 @@ https://leetcode.cn/problems/sequence-reconstruction/
 
 https://leetcode.cn/problems/ur2n8P/
 
+https://leetcode.cn/problems/fraction-addition-and-subtraction/
+
 #### 安装教程
 
 1. 安装`deno`

fraction-addition-and-subtraction/Fraction.ts

@@ -0,0 +1,26 @@
+export class Fraction {
+    sign: number;
+    molecular: number;
+    denominator: number;
+    toString() {
+        return `${
+            this.sign < 0 ? "-" : ""
+        }${this.molecular}/${this.denominator}`;
+    }
+    constructor({
+        sign = "+",
+        molecular = 1,
+        denominator = 1,
+    }: {
+        sign?: "+" | "-" | number;
+        molecular?: number | string;
+        denominator?: number | string;
+    } = {}) {
+        sign = sign || "+";
+        this.sign = (sign === "+" ? 1 : sign === "-" ? -1 : sign) *
+            Math.sign(Number(denominator)) *
+            Math.sign(Number(molecular));
+        this.molecular = Math.abs(Number(molecular));
+        this.denominator = Math.abs(Number(denominator));
+    }
+}

fraction-addition-and-subtraction/deduplication.ts

@@ -0,0 +1,3 @@
+export function deduplication<T>(iter: Iterable<T>): Array<T> {
+    return Array.from(new Set(iter));
+}

fraction-addition-and-subtraction/index.ts

@@ -0,0 +1,21 @@
+import { greatest_common_divisor } from "../max-points-on-a-line/greatest_common_divisor.ts";
+import { deduplication } from "./deduplication.ts";
+import { Fraction } from "./Fraction.ts";
+import { parseFraction } from "./parseFraction.ts";
+function fractionAddition(expression: string): string {
+    const fractions = parseFraction(expression);
+
+    const denominator = deduplication(
+        fractions.map((f) => f.denominator),
+    ).reduce((a, b) => a * b);
+    const molecular = fractions
+        .map((f) => (f.sign * f.molecular * denominator) / f.denominator)
+        .reduce((a, b) => a + b);
+    const gcd = greatest_common_divisor(molecular, denominator);
+
+    return new Fraction({
+        denominator: denominator / gcd,
+        molecular: molecular / gcd,
+    }).toString();
+}
+export default fractionAddition;

fraction-addition-and-subtraction/parseFraction.ts

@@ -0,0 +1,9 @@
+import { Fraction } from "./Fraction.ts";
+
+export function parseFraction(expression: string): Array<Fraction> {
+    return Array.from(
+        expression.matchAll(
+            /(?<sign>[+-]?)(?<molecular>\d+)\/(?<denominator>\d+)/g,
+        ),
+    ).map((a) => new Fraction(a.groups));
+}

fraction-addition-and-subtraction/test.ts

@@ -0,0 +1,11 @@
+import { assertEquals } from "https://deno.land/[email protected]/testing/asserts.ts";
+import fractionAddition from "./index.ts";
+Deno.test("fraction-addition-and-subtraction", () => {
+    assertEquals(
+        "77464/145635",
+        fractionAddition("100/399-133/2555-1/2+1/2-1/2+1/2+1/3"),
+    );
+    assertEquals("0/1", fractionAddition("-1/2+1/2"));
+    assertEquals("1/3", fractionAddition("-1/2+1/2+1/3"));
+    assertEquals("-1/6", fractionAddition("1/3-1/2"));
+});

max-points-on-a-line/greatest_common_divisor.ts

@@ -1,3 +1,3 @@
-export const greatest_common_divisor = (a: number, b: number): number => {
+export function greatest_common_divisor(a: number, b: number): number {
     return b != 0 ? greatest_common_divisor(b, a % b) : a;
-};
+}