一、题目
Given an integer array nums, return the third distinct maximum number in this array. If the third maximum does not exist, return the maximum number.
Example 1:
Input: nums = [3,2,1]
Output: 1
Explanation:
The first distinct maximum is 3.
The second distinct maximum is 2.
The third distinct maximum is 1.
Example 2:
Input: nums = [1,2]
Output: 2
Explanation:
The first distinct maximum is 2.
The second distinct maximum is 1.
The third distinct maximum does not exist, so the maximum (2) is returned instead.
Example 3:
Input: nums = [2,2,3,1]
Output: 1
Explanation:
The first distinct maximum is 3.
The second distinct maximum is 2 (both 2’s are counted together since they have the same value).
The third distinct maximum is 1.
Constraints:
1 <= nums.length <= 104
-231 <= nums[i] <= 231 - 1
Follow up: Can you find an O(n) solution?
二、题解
class Solution {
public:
int thirdMax(vector<int>& nums) {
set<int> s;
for(auto x:nums){
s.insert(x);
if(s.size() > 3) s.erase(s.begin());
}
return s.size() == 3 ? *s.begin() : *s.rbegin();
}
};
