Day number of year

.vscode/createNewProblem.sh

@@ -31,7 +31,7 @@ cp -R "$SRC_DIR" "$DEST_DIR"
 # --- rename files inside the copied folder ---
 # 1) Rename a specific file
 if [[ -f "$DEST_DIR/template.test.ts" ]]; then
-  mv "$DEST_DIR/template.test.ts" "$DEST_DIR/${NAME}.test.ts"
+  mv "$DEST_DIR/template.test.ts" "$DEST_DIR/${NAME,,}.test.ts"
 fi
 
 

Problems/Day-Number-Of-Year/Day-Number-Of-Year.test.ts

@@ -1,13 +1,54 @@
 import { describe, expect, it } from "vitest";
+import dayOfYear from "./solver";
 
-describe("Description for the tests", () => {
-	it("should return something for this input", () => {
-		expect(true).toEqual(true);
+describe("Returns the correct day number of the year", () => {
+	it("should return 348 for 12/13/2020", () => {
+		expect(dayOfYear("12/13/2020")).toEqual(348);
+	});
+
+	it("should return 321 for 11/16/2020", () => {
+		expect(dayOfYear("11/16/2020")).toEqual(321);
+	});
+
+	it("should return 9 for 1/9/2019", () => {
+		expect(dayOfYear("1/9/2019")).toEqual(9);
+	});
+
+	it("should return 61 for 3/1/2004", () => {
+		expect(dayOfYear("3/1/2004")).toEqual(61);
+	});
+
+	it("should return 366 (leap) for 12/31/2000", () => {
+		expect(dayOfYear("12/31/2000")).toEqual(366);
+	});
+
+	it("should return 365 for 12/31/2019", () => {
+		expect(dayOfYear("12/31/2019")).toEqual(365);
+	});
+
+	it("should return 2 for 1/2/2019", () => {
+		expect(dayOfYear("1/2/2019")).toEqual(2);
 	});
 });
 
-describe("Another description for the tests. Maybe those which are throwing errors", () => {
-	it("should return something for this input", () => {
-		expect(true).toEqual(true);
+describe("Catches a wrong date formate", () => {
+	it("should throw a error for 14/13/2020", () => {
+		expect(() => dayOfYear("14/13/2020")).toThrowError("The Month 14 isn't a valid Month!");
+	});
+
+	it("should throw a error for 11/31/2020", () => {
+		expect(() => dayOfYear("11/31/2020")).toThrowError("The 11 has only 30 days!");
+	});
+
+	it("should throw a error for 1/40/2020", () => {
+		expect(() => dayOfYear("1/40/2020")).toThrowError("The day 40 does not exist in any Month!");
+	});
+
+	it("should throw a error for 2/29/2019", () => {
+		expect(() => dayOfYear("2/29/2019")).toThrowError("February has only 28 days (No Leap)");
+	});
+
+	it("should throw a error for 2/30/2020", () => {
+		expect(() => dayOfYear("2/30/2020")).toThrowError("February has only 29 days");
 	});
 });

Problems/Day-Number-Of-Year/README.md

@@ -0,0 +1,54 @@
+# Day-Number-Of-Year
+
+You’re given a date string in the format month/day/year, based on the Gregorian calendar. Your task is to return which day of the year that date corresponds to (1–365, or 1–366 for leap years).
+
+## Infos which are maybe needed
+
+`January`, `March`, `May`, `July`, `August`, `October`, `December` are the months which have 31 days. `April`, `June`, `September`, `November` are the months which have 30 days. February has 28 days and in a leap year it has 29 days. Leap year is a year which divides by 4 but not 100 unless also divisible by 400.
+
+## Documentation
+
+### Solution Idea
+
+The idea is to use a counter variable that counts the total number of days.
+
+The counter starts with the number of days that have passed in the current month.  
+Then, a loop iterates over every month before the current month and adds the number of days each of those months had.
+
+After the loop finishes, the counter contains the total number of days that have passed since the beginning of the year.
+
+---
+
+### [Implementation](./solver.ts)
+
+First, we check whether the given day is between 1 and 31.  
+After that, we determine whether the given year is a leap year.
+
+To do this, we check if the year is divisible by 4 but not by 100.  
+If this condition is not met, we additionally check whether the year is divisible by 400.  
+With these checks we can determine whether the given year is a leap year.
+
+Next, we use a switch case to verify that the given month has a valid number of days.  
+For example, if the month is January, the day must not be greater than 31.
+
+If the date is valid, we create a day counter that starts with the given day.
+
+Then we start a loop that runs from `month - 1` down to `1`.  
+For each month, we add the number of days that month has to the counter.
+
+This is determined as follows:
+
+- We keep a list of months that have 30 days.
+- We keep another list of months that have 31 days.
+- For February, we check whether the year is a leap year.
+  - If it is a leap year, we add 29 days.
+  - Otherwise, we add 28 days.
+
+At the end we return the day counter.
+
+---
+
+### Information's
+
+This problem comes from the newsletter [Sloth Bytes](https://slothbytes.beehiiv.com).
+[Post](https://slothbytes.beehiiv.com/p/being-wrong-is-your-job) from December 02, 2025.

Problems/Day-Number-Of-Year/solver.ts

@@ -0,0 +1,72 @@
+export default function dayOfYear(date: string): number {
+	const [month, day, year] = date.split("/").map(Number);
+
+	if (day <= 0 || day > 31) throw new Error(`The day ${day} does not exist in any Month!`);
+
+	// Check if leap year
+	const leap = (year % 4 === 0 && year % 100 !== 0) || year % 400 === 0;
+	switchMonth(
+		month,
+		() => {},
+		() => {
+			if (day > 30) throw new Error(`The ${month} has only 30 days!`);
+		},
+		() => {
+			if (!leap && day > 28) throw new Error("February has only 28 days (No Leap)");
+			if (day > 29) throw new Error("February has only 29 days");
+		}
+	);
+
+	let dayCount = day;
+
+	for (let m = month - 1; m >= 1; m--) {
+		switchMonth(
+			m,
+			() => {
+				dayCount = dayCount + 31;
+			},
+			() => {
+				dayCount = dayCount + 30;
+			},
+			() => {
+				if (!leap) dayCount = dayCount + 28;
+				else dayCount = dayCount + 29;
+			}
+		);
+	}
+
+	return dayCount;
+}
+
+function switchMonth(
+	month: number,
+	func31: (month?: number) => void,
+	func30: (month?: number) => void,
+	func2: (month?: number) => void
+) {
+	switch (month) {
+		case 1:
+		case 3:
+		case 5:
+		case 7:
+		case 8:
+		case 10:
+		case 12: {
+			func31(month);
+			break;
+		}
+		case 4:
+		case 6:
+		case 9:
+		case 11: {
+			func30(month);
+			break;
+		}
+		case 2: {
+			func2(month);
+			break;
+		}
+		default:
+			throw new Error(`The Month ${month} isn't a valid Month!`);
+	}
+}

README.md

@@ -8,9 +8,9 @@ This repository is about solving coding-problems. It contains famous (or not tha
 
 ## Problems
 
-Solved: **21 problems**
+Solved: **22 problems**
 
-🟢 Easy: 15  
+🟢 Easy: 16  
 🟠 Medium: 5  
 🔴 Hard: 1
 
@@ -37,6 +37,7 @@ Solved: **21 problems**
 | [Sleep Time](./Problems/Sleep-Time/README.md)                                           | 🟢 Easy    |
 | [Reach Exit](./Problems/Reach-Exit/README.md)                                           | 🟢 Easy    |
 | [One Two Skip a Few](./Problems/One-Two-Skip-A-Few/README.md)                           | 🟢 Easy    |
+| [Day number of year](./Problems/Day-Number-Of-Year/README.md)                           | 🟢 Easy    |
 
 <!-- PROBLEMS_END -->
 

biome.jsonc

@@ -11,6 +11,9 @@
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 	},
+	"files": {
+		"includes": ["**", "!!package.json", "!!package-lock.json"]
+	},
 	"linter": {
 		"enabled": true,
 		"rules": {