Solutions to Leet Code Problems

is-palindrom-num.ts

function isPalindrome(num: number): boolean {
    let reversedNum = 0;
    let x = num;
    while (x > 0) {
        reversedNum = reversedNum * 10 + x % 10;
        x = x / 10 >> 0; // >> removes decimal
    }
    return reversedNum === num;
};

roman-integer.ts

const romanNumberMap = {
    'I': 1,
    'V': 5,
    'X': 10,
    'L': 50,
    'C': 100,
    'D': 500,
    'M': 1000
}

const isExceptionalRoman = (currentLetter: string, nextLetter: string): boolean => {
    return currentLetter === 'I' && ['V', 'X'].includes(nextLetter)
            || currentLetter === 'X' && ['C', 'L'].includes(nextLetter)
            || currentLetter === 'C' && ['M', 'D'].includes(nextLetter)
}

function romanToInt(s: string): number {
    let output = 0;
    let i = 0;
    while (i < s.length) {
        const nextLetter = s[i + 1];
        const currentLetter = s[i];
        if (isExceptionalRoman(currentLetter, nextLetter)) {
            output += romanNumberMap[nextLetter] - romanNumberMap[currentLetter];
            i += 2;
        } else {
            output += romanNumberMap[currentLetter];
            i++;
        }
    }
    return output;
};

single-pair-sum-target.ts

function twoSum(nums: number[], target: number): number[] {
    const numbersHashMap = {} as Record<number, number>;
    for (let i = 0; i < nums.length; i++) {
        const num = nums[i];
        const diff = target - num;
        if (diff in numbersHashMap) {
            return [numbersHashMap[diff], i];
        }
        numbersHashMap[num] = i;
    }
    return [];
};