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) {        long Max = LONG_MIN, Max2 = LONG_MIN, Max3 = LONG_MIN;        for(auto num: nums)        {            if(num > Max)            {                if(Max2!=LONG_MIN) Max3 = Max2;                if(Max!=LONG_MIN) Max2 = Max;                Max = num;            }            else if(num > Max2 && num!= Max)            {                if(Max2!=LONG_MIN) Max3 = Max2;                Max2 = num;            }            else if(num > Max3 && num!= Max && num!=Max2) Max3 = num;        }        return Max3==LONG_MIN?Max:Max3;       }};