[leetcode]565. Array Nesting_write a function solution that, given an array a c-优快云博客

本文介绍了一个LeetCode上的经典算法题——数组嵌套问题，并提供了一种高效的解决方案。该问题要求找出给定数组中最大不重复元素集合的大小。

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题目链接：https://leetcode.com/problems/array-nesting/#/description

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:

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

class Solution {
public:
    int arrayNesting(vector<int>& nums) {
        int res=0;
        for(int i=0;i<nums.size();i++)
        {
            if(nums[i]!=INT32_MAX)
            {
                int start=nums[i],count=0;
                while(nums[start]!=INT32_MAX)
                {
                    int temp=start;
                    start=nums[start];
                    count++;
                    nums[temp]=INT32_MAX;
                }
                res=max(res,count);
            }
        }
        return res;
    }
};