The k-digit number N is an Armstrong number if and only if the k-th power of each digit sums to N.
Given a positive integer N, return true if and only if it is an Armstrong number.
Example 1:
Input: 153 Output: true Explanation: 153 is a 3-digit number, and 153 = 1^3 + 5^3 + 3^3.
Example 2:
Input: 123 Output: false Explanation: 123 is a 3-digit number, and 123 != 1^3 + 2^3 + 3^3 = 36.
Note:
1 <= N <= 10^8