// Returns true if number is a palindrome, otherwise returns false
const isPalindrome = (num: number) => {
    // Convert to string so we can analyse the digits easier
    // There is probably a 'mathsy' way to work this out without converting
    let numberAsString = num.toString();

    // i is cursor (pointer) going left to right
    // j is cursor (pointer) going right to left
    let i = 0;
    let j = numberAsString.length;

    // Adding just in case
    if (num < 0) return false;

    // Keep comparing leftmost and rightmost characters at same intervals,
    // from beginning and end of string (originally number) until finished or a non-match is found
    while (i<=j){
        if (numberAsString.substring(i, i + 1) != numberAsString.substring(j - 1, j)){
            return false;
        }
        i++;
        j--;
    }
    return true;
}

// Finds a sum of all palindromic numbers,
// which must be at least as large as the 'target' specified
// and a palindrome in itself
// Returns the number of palindromes used to find the sum
const findSum = (target) => {
    let accumulator = 0;
    let i = 0;

    // Loop continuously until we reach the target
    // Alternatively we could add an upper bound (such as the 'target' itself)
    // to be extra careful of avoiding an infinite loop condition
    while(true){
        if (accumulator > target && isPalindrome(accumulator)) break;
        if (isPalindrome(i)) accumulator += i;
        i++;
    }
    return i;
}

// A few quick checks to make sure our function works as expected
// Should print 'true' for all
const isPalindrome_test = () => {
    console.log(true === isPalindrome(1231321));
    console.log(true === isPalindrome(171171));
    console.log(true === isPalindrome(11));
    console.log(true === isPalindrome(0));
    console.log(true === isPalindrome(1));
    console.log(true === isPalindrome(123456787654321));
    console.log(false === isPalindrome(522));
    console.log(false === isPalindrome(13213));
    console.log(false === isPalindrome(-25));
    console.log(false === isPalindrome(-131));
    console.log(false === isPalindrome(12333521));
    console.log(false === isPalindrome(1234577654321));
}

const findSum_test = () => {
    console.log(findSum(1000000))
}


//isPalindrome_test();
findSum_test();