Palindrome Number time limit exceeded error dart - dart

Question

First i want to say that i am trying to solve Palindrome Number problem on LeetCode using dart, of course
https://leetcode.com/problems/palindrome-number/
So far I have tried total 6 different method to solve the problem.
And am not very happy to say that all of them leading to time limit exceeded error on LeetCode.. Solutions are perfectly working on terminal because of the less test cases but when submit, and it tried on large number it ends up error.
My 6 solutions based on different classes.each class contain their own implemented solution..
I dont know if the while loop in dart is slow or something wrong with the leetcode
class A {
bool isPalindrome(int x) {
if (x < 0) {
return false;
}
double divisor = 1;
while (x / divisor >= 10) {
divisor *= 10;
}
while (x != 0) {
if ((x / divisor).truncate() != (x % 10).floor()) {
return false;
}
x %= divisor.toInt();
x = (x / 10).floor();
divisor /= 100;
}
return true;
}
}
class B {
bool isPalindrome(int x) {
if (x < 0 || (x % 10 == 0 && x != 0)) {
return false;
}
int revNum = 0;
while (x > revNum) {
revNum = revNum * 10 + x % 10;
x = (x / 10).floor();
}
return (x == revNum || x == revNum / 10);
}
}
class C {
bool isPalindrome(int x) {
if (x < 0) {
return false;
}
int y = 0;
int xx = x;
if (xx > 0) {
y = y * 10 + xx % 10;
xx = (xx / 10).floor();
}
return (y != x);
}
// while (xx > 0) {
// y = y * 10 + xx % 10;
// xx = (xx / 10).floor();
// }
}
class D {
bool isPalindrome(int x) {
if (x.isNegative) return false;
final list = convert(x);
for (var i = 0; i < (list.length ~/ 2); i++) {
if (list[i] != list[list.length - 1 - i]) return false;
}
return true;
}
List convert(int x) {
final List<int> list = <int>[];
while (x > 0) {
list.add(x % 10);
x = x ~/ 10;
}
return list;
}
}
class F {
bool isPalindrome(int x) {
if (x.isNegative) return false;
if (x == 0) return true;
if (x % 10 == 0) return false;
var reverted = 0, iter = x;
while (iter > 0) {
reverted = reverted * 10;
reverted += iter % 10;
iter = iter ~/ 10;
}
return reverted == x;
}
}
class G {
bool isPalindrome(int x) {
if (x.isNegative) return false;
var tens = 10;
while (tens < x) tens *= 10;
tens = tens ~/ 10;
while (x > 10) {
var lastDigit = x % 10;
var firstDigit = x ~/ tens;
if (lastDigit != firstDigit) return false;
x -= firstDigit * tens;
x = x ~/ 10;
tens = tens ~/ 100;
}
return true;
}
}

Answer 1

I'm pretty sure the leetcode site has a problem here.
I don't know what they're using their time on, but it seems impossible to get a correct result without a timeout.
My attempted solutions are:
class Solution2 {
// No intermediate allocations, only number operations.
bool isPalindrome(int x) {
if (x < 0) return false;
if (x < 10) return true;
int r = 0;
do {
var d = x.remainder(10);
x = x ~/ 10;
if (r == x) return true; // Odd length number
r = r * 10 + d;
if (r == x) return true; // Even length number
if (r == 0) return false; // Trailing zero
} while (r < x);
return false;
}
}
class Solution3 {
// Just do toString and check that it's a palindrome.
// Integer.toString is heavily optimized already.
bool isPalindrome(int x) {
if (x < 0) return false;
if (x < 10) return true;
var s = x.toString();
for (var i = 0, j = s.length - 1; i < j; i++, j--) {
if (s.codeUnitAt(i) != s.codeUnitAt(j)) return false;
}
return true;
}
}
If those are not fast enough, I seriously doubt anything will be.
I even considered whether repeatedly dividing by 10 was incredibly slow for some reason, so I switched to dividing by 100 instead, which should halve the divisions.
class Solution {
// Minimize divisions by dividing by 100, and do lookup for the digits.
static const digits =[
0, 0, 0, 1, 0, 2, 0, 3, 0, 4, 0, 5, 0, 6, 0, 7, 0, 8, 0, 9,
1, 0, 1, 1, 1, 2, 1, 3, 1, 4, 1, 5, 1, 6, 1, 7, 1, 8, 1, 9,
2, 0, 2, 1, 2, 2, 2, 3, 2, 4, 2, 5, 2, 6, 2, 7, 2, 8, 2, 9,
3, 0, 3, 1, 3, 2, 3, 3, 3, 4, 3, 5, 3, 6, 3, 7, 3, 8, 3, 9,
4, 0, 4, 1, 4, 2, 4, 3, 4, 4, 4, 5, 4, 6, 4, 7, 4, 8, 4, 9,
5, 0, 5, 1, 5, 2, 5, 3, 5, 4, 5, 5, 5, 6, 5, 7, 5, 8, 5, 9,
6, 0, 6, 1, 6, 2, 6, 3, 6, 4, 6, 5, 6, 6, 6, 7, 6, 8, 6, 9,
7, 0, 7, 1, 7, 2, 7, 3, 7, 4, 7, 5, 7, 6, 7, 7, 7, 8, 7, 9,
8, 0, 8, 1, 8, 2, 8, 3, 8, 4, 8, 5, 8, 6, 8, 7, 8, 8, 8, 9,
9, 0, 9, 1, 9, 2, 9, 3, 9, 4, 9, 5, 9, 6, 9, 7, 9, 8, 9, 9,
];
bool isPalindrome(int x) {
if (x < 0) return false;
if (x < 10) return true;
int r = 0;
do {
var d = x.remainder(100);
x = x ~/ 100;
var d1 = digits[d * 2];
var d2 = digits[d * 2 + 1];
if (r == x && d1 == d2) return true; // Even length number
if (r == x * 10 + d1) return true; // Odd length number.
r = r * 10 + d2;
if (r == 0) return false; // Trailing zero
if (r == x) return true; // Odd length number
r = r * 10 + d1;
if (r == x) return true; // Even length number
} while (r < x);
return false;
}
}
Still times out.