#C3584. Convergence of Digit Square Sum Sequence
Convergence of Digit Square Sum Sequence
Convergence of Digit Square Sum Sequence
Given an integer \(a_0\) and an integer \(K\), define a sequence \(a_0, a_1, a_2, \ldots\) where each subsequent term is the sum of the squares of the digits of the previous term. In particular, the transformation can be written in LaTeX as:
\( a_{n+1} = \sum_{d \in D(a_n)} d^2 \),
where \(D(a_n)\) denotes the set of digits of \(a_n\). Your task is to determine if the sequence reaches the value 1 within \(K\) steps (including the possibility that \(a_0 = 1\)). If the sequence reaches 1 within \(K\) steps, print YES
, otherwise print NO
.
Note: The operation should be applied at most \(K\) times. For example, if \(a_0 = 19\) and \(K = 10\), the sequence eventually reaches 1, so the answer is YES
.
inputFormat
The input is given via standard input (stdin) and is formatted as follows:
- The first line contains a single integer \(T\) representing the number of test cases.
- The following \(T\) lines each contain two space-separated integers \(a_0\) and \(K\), where \(a_0\) is the starting integer and \(K\) is the maximum number of steps allowed.
outputFormat
For each test case, output a single line containing either YES
if the sequence reaches 1 within \(K\) steps or NO
otherwise. The output should be printed via standard output (stdout).
3
19 10
82 5
7 2
YES
YES
NO
</p>