# [414. Third Maximum Number](https://leetcode.com/problems/third-maximum-number/) ## 题目 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. ## 题目大意 给定一个非空数组,返回此数组中第三大的数。如果不存在,则返回数组中最大的数。要求算法时间复杂度必须是 O(n)。 ## 解题思路 - 水题,动态维护 3 个最大值即可。注意数组中有重复数据的情况。如果只有 2 个数或者 1 个数,则返回 2 个数中的最大值即可。