LeetCode: Super Palindromes Solution

1/**
2 * @param {string} left
3 * @param {string} right
4 * @return {number}
5 */
6var superpalindromesInRange = function (left, right) {
7 ;[left, right] = [+left, +right]
8
9 const isPalindrome = s => s === s.split("").reverse().join("")
10
11 let palindromes = [1, 2, 3, 4, 5, 6, 7, 8, 9]
12 // as range is max of 1e18 => find from sqrt(1e18) = 1e9
13 // build palindrome from concatnate: xx, x0x, x1x,...x9x
14 // so x must be in range 9/2 = 4
15 for (let i = 1; i < 10000; i++) {
16 const s1 = String(i) + String(i).split("").reverse().join("")
17 palindromes.push(s1)
18 for (let j = 0; j < 10; j++) {
19 const s2 = String(i) + String(j) + String(i).split("").reverse().join("")
20 palindromes.push(s2)
21 }
22 }
23
24 palindromes = palindromes.map(Number).sort((a, b) => a - b)
25
26 let numberOfSuperPalindromesInRange = 0
27
28 for (const palindrome of palindromes) {
29 const s = String(BigInt(palindrome) ** 2n)
30 if (isPalindrome(s) && left <= Number(s) && Number(s) <= right) {
31 numberOfSuperPalindromesInRange++
32 }
33 }
34
35 return numberOfSuperPalindromesInRange
36}

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leetcode

math

string

array

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