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  • 565. Array Nesting 阵列嵌套


    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: 6Explanation: 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].


    1. /**
    2. * @param {number[]} nums
    3. * @return {number}
    4. */
    5. var arrayNesting = function (nums) {
    6.    let res = 0, set = new Set();           //因为集合S会成环,因此可以用set存储遍历过的index
    7.    for (let i = 0; i < nums.length; i++) {
    8.        let curIndex = i, count = 0;
    9.        while (!set.has(curIndex)) {
    10.            set.add(curIndex);
    11.            curIndex = nums[curIndex];
    12.            count++;
    13.        }
    14.        res = Math.max(res, count);
    15.    }
    16.    return res;
    17. };
    18. //let arr = [5, 4, 0, 3, 1, 6, 2];
    19. let arr = [1, 2, 3, 4, 5, 0]
    20. console.log(arrayNesting(arr));






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  • 原文地址:https://www.cnblogs.com/xiejunzhao/p/8045107.html
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