Leetcode 155. 最小栈 辅助栈

原题链接：Leetcode 155. 最小栈

官方解法：辅助栈

class MinStack {
    stack<int> st;
    stack<int> minst;
public:
    MinStack() {
        minst.push(INT_MAX);
    }
    
    void push(int val) {
        st.push(val);
        minst.push(min(minst.top(),val));
    }
    
    void pop() {
        st.pop();
        minst.pop();
    }
    
    int top() {
        return st.top();
    }
    
    int getMin() {
        return minst.top();
    }
};

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

一个栈同时保存当前值和栈内最小值

class MinStack {
    stack<pair<int,int>> st;
public:
    MinStack() {
        st.push({-1,INT_MAX});
    }
    
    void push(int val) {
        st.push({val,min(getMin(),val)});
    }
    
    void pop() {
        st.pop();
    }
    
    int top() {
        return st.top().first;
    }
    
    int getMin() {
        return st.top().second;
    }
};

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