LeetCode：M-565. Array Nesting

LeetCode链接

A zero-indexed array A consisting of N different integers is given. The array contains all integers in the range [0, N - 1].

Sets S[K] for 0 <= K < N are defined as follows:

S[K] = { A[K], A[A[K]], A[A[A[K]]], ... }.

Sets S[K] are finite for each K and should NOT contain duplicates.

Write a function that given an array A consisting of N integers, return the size of the largest set S[K] for this array.

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 array A is an integer within the range [0, N-1].

1、原有数组，其实类似于数组形式表示的链表

2、遍历链表，遍历过的node设置为-1，直到链表下一个遇到访问过得node，则得出了一条链表的长度

3、继续遍历没有访问过的其他链表

class Solution {
    public int arrayNesting(int[] nums) {
        if(nums==null) return 0;
        
        int max=0;
        for(int i=0; i<nums.length; i++){//继续遍历没有访问过的其他链表
            if(nums[i]==-1)
                continue;
            
            int cnt=0;
            int j=i;
            while(nums[j]!=-1){ //遍历链表，遍历过的node设置为-1，直到链表下一个遇到访问过得node，则得出了一条链表的长度               
                int tmp = j;
                cnt++;
                j=nums[j];
                nums[tmp]=-1;
                
            }
            max = Math.max(max, cnt);
        }
        
        return max;
    }
}