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  • LeetCode : Third Maximum Number

    Given a non-empty array of integers, return the third maximum number in this array. If it does not exist, return the maximum number. The time complexity must be in O(n).

    Example 1:
    Input: [3, 2, 1]

    Output: 1

    Explanation: The third maximum is 1.
    Example 2:
    Input: [1, 2]

    Output: 2

    Explanation: The third maximum does not exist, so the maximum (2) is returned instead.
    Example 3:
    Input: [2, 2, 3, 1]

    Output: 1

    Explanation: Note that the third maximum here means the third maximum distinct number.
    Both numbers with value 2 are both considered as second maximum.

    class Solution {
    public:
        int thirdMax(vector<int>& nums) {
            set<int> s;
            for (int num : nums) {
                s.insert(num);
                if (s.size() > 3) {
                    s.erase(s.begin());
                }
            }
            return s.size() == 3 ? *s.begin() : *s.rbegin();
        }
    };
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  • 原文地址:https://www.cnblogs.com/chankeh/p/6850048.html
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