Lightnews — Scholar-powered news

Muhammad Khan

@muhammadkhan.dev

github.com/muhammadk160...

export const sumOfNeighbors = (arr: number[]): number => {
let sum = 0;

for (let i = 0; i < arr.length; i++) {
sum += (arr[i - 1] || 0) + (arr[i] || 0) + (arr[i + 1] || 0);
}

return sum;
};

September 8, 2025 at 6:32 AM

Muhammad Khan

@muhammadkhan.dev

github.com/muhammadk160...

Hexagons are Bestagons!

export const canFormHexagon = (sides: number[]): boolean => {
if (sides.length !== 6) return false;

const sideCount: Record<number, number> = {};
for (const side of sides) {
sideCount[side] = (sideCount[side] || 0) + 1;
}

return Object.values(sideCount).filter(count => count >= 2).length === 3;
};

July 28, 2025 at 8:21 AM

Muhammad Khan

@muhammadkhan.dev

github.com/muhammadk160...

export const nonRepeat = (str: string): string => {
const charCount: Record<string, number> = {};

for (const char of str) {
charCount[char] = (charCount[char] || 0) + 1;
}

for (let i = str.length - 1; i >= 0; i--) {
const char = str[i] || "";
if (charCount[char] === 1) return char;
}

return "";
};

June 30, 2025 at 9:11 AM

Muhammad Khan

@muhammadkhan.dev

github.com/muhammadk160...

$const ROMAN_MAP = { I: 1, V: 5, X: 10, L: 50, C: 100, D: 500, M: 1000, } as const; const romanToInt = (roman: string): number => { let total = 0; let prevValue = 0; for (let i = roman.length - 1; i >= 0; i--) { const currentValue = ROMAN_MAP[roman[i] as keyof typeof ROMAN_MAP]; if (currentValue < prevValue) total -= currentValue; else total += currentValue; prevValue = currentValue; } return total; }; export const sortMonarchs = (monarchs: string[]): string[] => { return monarchs.sort((a, b) => { const [nameA, ordinalA] = a.split(" ") as [string, string]; const [nameB, ordinalB] = b.split(" ") as [string, string]; const numberA = romanToInt(ordinalA); const numberB = romanToInt(ordinalB); // If years are the same, compare by name return nameA.localeCompare(nameB) || numberA - numberB; }); };$

June 16, 2025 at 7:23 AM

Muhammad Khan

@muhammadkhan.dev

github.com/muhammadk160...

export type TrafficLight = "red" | "green" | "yellow";
export const isValidTrafficSequence = (sequence: TrafficLight[]): boolean => {
let prevLight: TrafficLight | null = null;

for (let i = 0; i < sequence.length; i++) {
const light = sequence[i] as TrafficLight;

if (prevLight === "red" && light !== "green") return false;
if (prevLight === "green" && light !== "yellow") return false;
if (prevLight === "yellow" && light !== "red") return false;

prevLight = light;
}

return true;
};

June 10, 2025 at 6:39 AM

Muhammad Khan

@muhammadkhan.dev

github.com/muhammadk160...

I have only one question regarding this task: "But why?"

export const nestArray = (array: any[]): any[] => {
const result: any[] = [];
let current = result;

for (let i = 0; i < array.length; i++) {
current.push(array[i]);

if (i === array.length - 1) break;

const nextLevel: any[] = [];
current.push(nextLevel);
current = nextLevel;
}

return result;
};

June 2, 2025 at 12:50 PM

Muhammad Khan

@muhammadkhan.dev

github.com/muhammadk160...

export const oddSum = (first: number[], second: number[]): number[][] => {
const result: number[][] = [];

first.forEach(x => {
second.forEach(y => {
if ((x + y) % 2 !== 0) {
result.push([x, y]);
}
});
});

return result;
};

May 30, 2025 at 1:29 PM

Muhammad Khan

@muhammadkhan.dev

Baseline shamelessly "borrowed" from @tenzhiyang.com

github.com/muhammadk160...

$const CORNER = "+"; const VERTICAL = "|"; const HORIZONTAL = "-"; const DIAGONAL = "/"; const SPACE = " "; const NUMBER_OF_HORIZONTAL_LINES = 3; export const drawCube = (size: number) => { const horizontalLine = Array.from({ length: size * 2 + 2 }) .map((_, i, { length }) => (i === 0 || i === length - 1 ? CORNER : HORIZONTAL)) .join(""); const padding = Math.floor(size / 2); const rows = Array.from({ length: size + NUMBER_OF_HORIZONTAL_LINES + padding }); return ( "\n" + rows .map((_, i, { length }) => { if (i === 0) { return SPACE.repeat(padding + 1) + horizontalLine; } else if (i > 0 && i < padding + 1) { return ( SPACE.repeat(padding + 1 - i) + DIAGONAL + SPACE.repeat(size * 2) + DIAGONAL + SPACE.repeat(Math.max(i - 1, 0)) + VERTICAL ); } else if (i === padding + 1) { return horizontalLine + SPACE.repeat(padding) + VERTICAL; } else if (i > padding + 1 && i < length - 1) { let endItem = VERTICAL; let paddingEnd = padding; if (i === size + 1) { endItem = CORNER; } if (i > size + 1) { endItem = DIAGONAL; paddingEnd = length - i - 2; } return VERTICAL + SPACE.repeat(size * 2) + VERTICAL + SPACE.repeat(paddingEnd) + endItem; } else if (i === length - 1) { return horizontalLine; } else { return SPACE; } }) .join("\n") + "\n" ); };$

May 20, 2025 at 6:14 AM

Muhammad Khan

@muhammadkhan.dev

github.com/muhammadk160...

export const addOperators = (origin: number, target: number): string[] => {
const digits = origin.toString().split("");
const result: string[] = [];

const dfs = (index: number, path: string, currentNumber: number) => {
if (index === digits.length) {
if (currentNumber === target) result.push(path);
return;
}

for (let i = index; i < digits.length; i++) {
const digit = digits[i];
const newNumber = Number(digit);

dfs(i + 1, `${path}+${digit}`, currentNumber + newNumber);
dfs(i + 1, `${path}-${digit}`, currentNumber - newNumber);

// Multiply but only if BODMAS is not violated
if (!(path.includes("+") || path.includes("-")))
dfs(i + 1, `${path}*${digit}`, currentNumber * newNumber);
}
};

// Start DFS from the first digit
const firstDigit = digits[0] as string;
const firstNumber = Number(firstDigit);
dfs(1, firstDigit, firstNumber);

return result;
};

May 16, 2025 at 12:26 PM

Muhammad Khan

@muhammadkhan.dev

"Never think that war, no matter how necessary, nor how justified, is not a crime." ~ Ernest Hemingway

I wish for calmer heads to prevail.

May 7, 2025 at 11:49 AM

Muhammad Khan

@muhammadkhan.dev

github.com/muhammadk160...

export const longestCommonPrefix = (strings: string[]): string => {
let prefix = strings[0] || "";

for (let i = 1; i < strings.length; i++) {
while (strings[i]?.indexOf(prefix) !== 0) {
prefix = prefix.slice(0, -1);
if (prefix === "") return "";
}
}

return prefix;
};

May 5, 2025 at 10:56 AM

Muhammad Khan

@muhammadkhan.dev

github.com/muhammadk160...

export const compress = (characters: string[]): string[] => {
const compressed: string[] = [];

let currentChar = characters[0] as string;
let count = 1;

for (let i = 1; i <= characters.length; i++) {
if (characters[i] === currentChar) {
count++;
} else {
compressed.push(currentChar);
if (count > 1) {
compressed.push(count.toString());
}
currentChar = characters[i] as string;
count = 1;
}
}

return compressed;
};

April 28, 2025 at 7:44 AM

Muhammad Khan

@muhammadkhan.dev

github.com/muhammadk160...

export type TIngredient = {
name: string;
amount: number;
};

export const calculateIngredients = (
ingredients: TIngredient[],
targetServings: number,
): TIngredient[] =>
ingredients.map(ingredient => ({
...ingredient,
amount: ingredient.amount * targetServings,
}));

April 21, 2025 at 7:43 AM

Muhammad Khan

@muhammadkhan.dev

I am starting to think that noUncheckedIndexedAccess rule is overkill.

github.com/muhammadk160...

const DIRECTIONS = [
[0, 1],
[1, 0],
[0, -1],
[-1, 0],
] as const;

export const largestPathSum = (grid: number[][]): number => {
const rows = grid.length;

if (!grid[0]) return 0;

const cols = grid[0].length;

let maxSum = 0;

function dfs(x: number, y: number, visited: boolean[][], currentSum: number) {
maxSum = Math.max(maxSum, currentSum);

for (const [dx, dy] of DIRECTIONS) {
const nx = x + dx;
const ny = y + dy;

if (!visited[nx] || !grid[nx]) continue;

if (nx >= 0 && ny >= 0 && nx < rows && ny < cols && !visited[nx][ny]) {
visited[nx][ny] = true;
dfs(nx, ny, visited, currentSum + (grid[nx][ny] || 0));
visited[nx][ny] = false;
}
}
}

for (let i = 0; i < rows; i++) {
for (let j = 0; j < cols; j++) {
const visited = Array.from({ length: rows }, () => Array(cols).fill(false));

// @ts-ignore
visited[i][j] = true;
// @ts-ignore
dfs(i, j, visited, grid[i][j]);
}
}

return maxSum;
};

April 16, 2025 at 10:33 AM

Muhammad Khan

@muhammadkhan.dev

github.com/muhammadk160...

const getLeylandNumbers = (n: number): number[] => {
let count = n;
let leylandNumbers: number[] = [];

let x = 2;

while (count > 0) {
for (let i = 2; i <= x; i++) {
leylandNumbers.push(Math.pow(i, x) + Math.pow(x, i));
}
x++;
count--;
}

return leylandNumbers.toSorted((a, b) => a - b).slice(0, n);
};

April 7, 2025 at 9:14 AM

Muhammad Khan

@muhammadkhan.dev

github.com/muhammadk160...

const getMinutes = (time: string): number => {
const [hours, minutes] = time.split(":").map(Number);

if (hours === undefined || minutes === undefined)
throw new Error(`Invalid time format: ${time}`);

return hours * 60 + minutes;
};

export const findLongestTimeGap = (times: string[]): number => {
let longestGap = 0;

for (let i = 0; i < times.length - 1; i++) {
const current = times[i] as string;
const next = times[i + 1] as string;

longestGap = Math.max(longestGap, getMinutes(next) - getMinutes(current));
}

return longestGap;
};

April 1, 2025 at 6:56 AM

Muhammad Khan

@muhammadkhan.dev

github.com/muhammadk160...

export const findLongestStreak = (values: boolean[]) => {
let max = 0;

for (let i = 0; i < values.length; i++) {
let current = 0;
while (values[i]) {
current++;
i++;
}

if (current > max) {
max = current;
}
}

return max;
}

March 25, 2025 at 10:09 AM

Muhammad Khan

@muhammadkhan.dev

Thanks for forcing me to learn some basic Music Theory 😀

github.com/muhammadk160...

const SEMITONES = {
C: 0,
D: 2,
E: 4,
F: 5,
G: 7,
A: 9,
B: 11,
};

export const findLargestInterval = (keys: string[]): number => {
const intervals = keys.map(key => {
const note = key[0] as keyof typeof SEMITONES;
const octave = Number(key[1]);
return SEMITONES[note] + octave * 12;
});

let largestInterval = 0;

for (let i = 0; i < intervals.length - 1; i++) {
const current = intervals[i] as number;
const next = intervals[i + 1] as number;

largestInterval = Math.max(largestInterval, Math.abs(current - next));
}

return largestInterval;
};

March 11, 2025 at 7:33 AM

Muhammad Khan

@muhammadkhan.dev

github.com/muhammadk160...

Skipped last week's problem since I felt like the solution I came up with wasn't mine. 😀

export const calculatePrice = (closingDate: string, visitDate: string, price: number): number => {
const closingDateTimestamp = new Date(closingDate).getTime();
const visitDateTimestamp = new Date(visitDate).getTime();

if (visitDateTimestamp > closingDateTimestamp) return price;

const weeks = Math.floor(
(closingDateTimestamp - visitDateTimestamp) / (1000 * 60 * 60 * 24 * 7),
);

for (let i = 0; i < weeks; i++) {
price -= price * 0.1;
}

return price;
};

March 3, 2025 at 8:32 AM

Muhammad Khan

@muhammadkhan.dev

github.com/muhammadk160...

export const findShieldBreak = (attacks: number[], shield: number): number => {
for (let i = 0; i < attacks.length; i++) {
shield -= attacks[i] as number;
if (shield < 0) return i;
}

return -1;
};

February 17, 2025 at 9:51 AM

Muhammad Khan

@muhammadkhan.dev

Just ran a 5k.

Not gonna lie, 50% of my motivation came just from seeing all these tech people running marathons.

Do I get to join the cool kids club now?