[LeetCode] 414. 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: 1Explanation: The third maximum is 1.

Example 2:

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

Example 3:

Input: [2, 2, 3, 1]Output: 1Explanation: 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) {        priority_queue<int> pq;        for (int i = 0; i < nums.size(); i++)            pq.push(nums[i]);        int max = pq.top(), thirdmax = pq.top(), tick = 2;        while (tick > 0 && !pq.empty()) {            if (pq.top() != thirdmax) {                thirdmax = pq.top();                tick--;            }            pq.pop();        }        return tick > 0 ? max : thirdmax;    }};