#3577

Count the Number of Computer Unlocking Permutations

specialist · 760 · lc medium +31 · 59% accepted · 355 likes · top 56%

Description

An integer array complexity of length n gives the password difficulty of n computers labeled 0 through n - 1.

Computer 0 starts already unlocked. To unlock computer i, you need a previously unlocked computer j where j < i and complexity[j] < complexity[i].

Count permutations of [0, 1, ..., n - 1] representing valid unlocking sequences starting from computer 0.

Return the count modulo 10⁹ + 7.

Note: label 0 refers to computer identity, not a position in the permutation.

Code

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class Solution:
    def countPermutations(self, complexity: List[int]) -> int:

class Solution:
    def countPermutations(self, complexity: List[int]) -> int: