[LeetCode] Min Stack

Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.

• push(x) -- Push element x onto stack.
• pop() -- Removes the element on top of the stack.
• top() -- Get the top element.
• getMin() -- Retrieve the minimum element in the stack.

这道题神烦，总是超过内存限制，思路就是那个但是就是内存超了，不明觉历，拿到要用c数组？

总之需要注意两点：

1.每个操作都要O(1)

2.pop了以后注意min的变化

class MinStack {
private:
    vector<int> min;
    vector<int> data;
public:
    void push(int x) {
        data.push_back(x);
        if (min.size() == 0 || data[min.at(min.size()-1)] > x) {
            min.push_back((int)data.size()-1);
        }
    }
    
    void pop() {
        if (data.size()) {
            if (min.size() > 0 && min.at(min.size()-1) == data.size()-1) {
                min.pop_back();
            }
            data.pop_back();
        }
    }
    
    int top() {
        if (data.size() > 0)
            return data.at(data.size()-1);
        return INT_MIN;
    }
    
    int getMin() {
        return data.at(min.at(min.size()-1));
    }
};