LeetCode 155. 最小栈

题目链接：155. 最小栈

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2020.10.15第一次解答：

解题思路

个人以为实现一个最小栈就不能用STL的栈，于是定义了一个链表结构体写的栈...一看题解，嗯？还能这样？

但是用自定义链表的速度就很快哈哈哈哈哈

 

C++代码

class MinStack {
private:
    int min;
    struct node {
        int val;
        node* pre;
    };
    node* cur;
public:
    /** initialize your data structure here. */
    MinStack() {
        min = INT_MAX;
        cur = nullptr;
    }
    
    void push(int x) {
        node* tmp = new node;
        if (!cur) {
            tmp->pre = nullptr;
            tmp->val = x;
        }
        else {
            tmp->pre = cur;
            tmp->val = x;
        }
        cur = tmp;
        if (x < min)    min = x;
    }
    
    void pop() {
        //需要考虑元素出栈后，最小栈值有没有改变
        if (cur->val == min) {
            int min2 = INT_MAX;
            node* tmp = cur->pre;
            while (tmp) {
                if (tmp->val < min2) {
                     min2 = tmp->val;
                }
                tmp = tmp->pre;
            }
            min = min2;
            delete(tmp);
        }
        node* tmp = cur;
        cur = cur->pre;
        delete(tmp);
    }
    
    int top() {
        return cur->val;
    }
    
    int getMin() {
        return min;
    }
};

/**
 * Your MinStack object will be instantiated and called as such:
 * MinStack* obj = new MinStack();
 * obj->push(x);
 * obj->pop();
 * int param_3 = obj->top();
 * int param_4 = obj->getMin();
 */