Good Subsequence
Practice
4.5 (2 votes)
Math
Observation
Basic math
C++
Problem
22% Success 417 Attempts 20 Points 1s Time Limit 256MB Memory 1024 KB Max Code
You are given an array \(A\) of length \(N\). A subsequence is called good if all the elements of that subsequence are distinct. Find the number of non-empty good subsequences modulo \(10^9+7\).
Two subsequences are different if they differ in the indices chosen.
Input Format:
- The first line contains an integer \(T\), which denotes the number of test cases.
- The first line of each test case contains an integer \(N\).
- The second line of each test case contains \(N\) space-separated integers, elements of array \(A\).
Output Format:
For each test case, print the number of non-empty good subsequences modulo \(10^9+7\).
Constraints:
\(1 \leq T \leq 10 \\ 1 \leq N \leq 10^5 \\ 1 \leq A[i] \leq 10^5\)
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