剑指offer 包含min函数的栈

class Solution {
private:
    vector<int> vec;
public:
    void push(int value) {
        vec.emplace_back(value);
    }
    void pop() {
        if(vec.empty()) return;
        vec.erase(vec.end()-1);
    }
    int top() {
        if(vec.empty()) return 0;
        return *(vec.end()-1);
    }
    int min() {
        if(vec.empty()) return 0;
        return *min_element(vec.begin(), vec.end());
    }
};