LeetCode in TypeScript
7. Reverse Integer
Medium
Given a signed 32-bit integer x, return x with its digits reversed. If reversing x causes the value to go outside the signed 32-bit integer range [-231, 231 - 1], then return 0.
Assume the environment does not allow you to store 64-bit integers (signed or unsigned).
Example 1:
Input: x = 123
Output: 321
Example 2:
Input: x = -123
Output: -321
Example 3:
Input: x = 120
Output: 21
Example 4:
Input: x = 0
Output: 0
Constraints:
-231 <= x <= 231 - 1
Solution
function reverse(x: number): number {
let remaining = Math.abs(x)
let power = Math.floor(Math.log10(remaining))
let reversed = 0
while (remaining > 0) {
const digit = remaining % 10
remaining = (remaining - digit) / 10
reversed += digit * 10 ** power--
if (reversed > 2 ** 31 - 1) return 0
}
return x > 0 ? reversed : -reversed
}
export { reverse }