题目：

题解：

class Solution {
public:int thirdMax(vector<int> &nums) {int *a = nullptr, *b = nullptr, *c = nullptr;for (int &num : nums) {if (a == nullptr || num > *a) {c = b;b = a;a = &num;} else if (*a > num && (b == nullptr || num > *b)) {c = b;b = &num;} else if (b != nullptr && *b > num && (c == nullptr || num > *c)) {c = &num;}}return c == nullptr ? *a : *c;}
};