Strange Function
의견: 0
For all positive integers \(x\), the function \(f(x)\) is defined as follows:
- If \(x\) has any digits that aren't \(0\) or \(1\), for each digit of \(x\), set it to \(1\) if it is odd or \(0\) otherwise, and return \(x\).
- Otherwise, return \(x-1\).
Given a value of \(x\) (\(1 \leq x < 10^{2\cdot 10^5}\)), find how many times \(f\)
needs to be applied to \(x\) until \(x\) reaches \(0\). As this number might be very
large, output its remainder when divided by \(10^9+7\).
Problem credits: Aidan Bai
SCORING
- Inputs 3-5: \(T\le 2000\), \(x< 10^{9}\)
- Inputs 6-7: \(x<10^{18}\)
- Inputs 8-9: \(x<10^{60}\)
- Inputs 10-12: No additional constraints.
Problem credits: Aidan Bai
The first line contains \(T\) (\(1\le T\le 10^5\)), the number of independent tests.
The next \(T\) lines each contain a positive integer \(x\) consisting solely of the
digits 0-9, with no leading zeros.
It is guaranteed that the total number of digits in all input integers does not
exceed \(10^6\).
For each test case, output the remainder of the number of times when divided by
\(10^9+7\) on a separate line.
2
24680
2101
4First test: \(x\) becomes zero after one operation.
Second test: \(f(x)=10, f^2(x)=9, f^3(x)=1, f^4(x)=0\)
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출처 올림피아드 > USACO > 2025-2026 > Third Contest > Bronze
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Strange Function
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Strange Function