|
| 1 | +# Time: O(n) |
| 2 | +# Space: O(1) |
| 3 | + |
| 4 | +# A zero-indexed array A consisting of N different integers is given. |
| 5 | +# The array contains all integers in the range [0, N - 1]. |
| 6 | +# |
| 7 | +# Sets S[K] for 0 <= K < N are defined as follows: |
| 8 | +# |
| 9 | +# S[K] = { A[K], A[A[K]], A[A[A[K]]], ... }. |
| 10 | +# |
| 11 | +# Sets S[K] are finite for each K and should NOT contain duplicates. |
| 12 | +# |
| 13 | +# Write a function that given an array A consisting of N integers, |
| 14 | +# return the size of the largest set S[K] for this array. |
| 15 | +# |
| 16 | +# Example 1: |
| 17 | +# Input: A = [5,4,0,3,1,6,2] |
| 18 | +# Output: 4 |
| 19 | +# Explanation: |
| 20 | +# A[0] = 5, A[1] = 4, A[2] = 0, A[3] = 3, A[4] = 1, A[5] = 6, A[6] = 2. |
| 21 | +# |
| 22 | +# One of the longest S[K]: |
| 23 | +# S[0] = {A[0], A[5], A[6], A[2]} = {5, 6, 2, 0} |
| 24 | +# Note: |
| 25 | +# N is an integer within the range [1, 20,000]. |
| 26 | +# The elements of A are all distinct. |
| 27 | +# Each element of array A is an integer within the range [0, N-1]. |
| 28 | + |
| 29 | +class Solution(object): |
| 30 | + def arrayNesting(self, nums): |
| 31 | + """ |
| 32 | + :type nums: List[int] |
| 33 | + :rtype: int |
| 34 | + """ |
| 35 | + result = 0 |
| 36 | + for num in nums: |
| 37 | + if num != None: |
| 38 | + start, count = num, 0 |
| 39 | + while nums[start] != None: |
| 40 | + temp = start |
| 41 | + start = nums[start] |
| 42 | + nums[temp] = None |
| 43 | + count += 1 |
| 44 | + result = max(result, count) |
| 45 | + return result |
| 46 | + |
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