【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.

思路：我分了三种情况，分别是数组长度为1,2以及2以上，对于第三种情况，也要考虑到不存在第三大数字的情况。

答案：

class Solution {
public:
    int thirdMax(vector<int>& nums)
{
sort(nums.begin(),nums.end());
int num=2;
if(nums.size()==1)
return nums[0];
else if(nums.size()==2)
return nums[1];
for(int i=nums.size()-2;i>=0;i--)
{
if(nums[i]!=nums[i+1])
num--;
if(num==0)
return nums[i];
if(i==0&&num!=0)
return nums[nums.size()-1];
}
}
};