Practice Valid Permutations for DI Sequence
Read the task, work through the examples, and check your approach against the constraints. Use the original LeetCode task for coding and submissions.
Problem Statement
For a string s of length n containing D and I, count permutations of all integers 0 through n that satisfy its comparisons. At position i, D requires perm[i] > perm[i + 1], while I requires perm[i] < perm[i + 1]. Return the count modulo 10^9 + 7.
Source: Valid Permutations for DI Sequence on LeetCode. Use the original task for its coding environment and submissions.
Examples
# Example 1
Input
s = "DID"
Output
5
# Example 2
Input
s = "D"
Output
1
Constraints
n == s.length
1 <= n <= 200
s[i] is either 'I' or 'D'.
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