565. Array Nesting

Problem:

A zero-indexed array A of length N contains all integers from 0 to N-1. Find and return the longest length of set S, where S[i] = {A[i], A[A[i]], A[A[A[i]]], ... } subjected to the rule below.

Suppose the first element in S starts with the selection of element A[i] of index = i, the next element in S should be A[A[i]], and then A[A[A[i]]]… By that analogy, we stop adding right before a duplicate element occurs in S.

Example 1:

Input: A = [5,4,0,3,1,6,2]
Output: 4
Explanation: 
A[0] = 5, A[1] = 4, A[2] = 0, A[3] = 3, A[4] = 1, A[5] = 6, A[6] = 2.

One of the longest S[K]:
S[0] = {A[0], A[5], A[6], A[2]} = {5, 6, 2, 0}

Note:

1. N is an integer within the range [1, 20,000].
2. The elements of A are all distinct.
3. Each element of A is an integer within the range [0, N-1].

思路：

Solution (C++):

int arrayNesting(vector<int>& nums) {
    int max_size = 0;
    for (int i = 0; i < nums.size(); ++i) {
        int size = 0;
        for (int j = i; nums[j] >= 0; ++size) {
            int tmp = nums[j];
            nums[j] = -1;
            j = tmp;
        }
        max_size = max(max_size, size);
    }
    return max_size;
}

性能：

Runtime: 12 ms  Memory Usage: 7.8 MB

思路：

Solution (C++):

性能：

Runtime: ms  Memory Usage: MB