LeetCode 155. Min Stack(Medium)#Stack

- 8月 16, 2021

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.

Example:

MinStack minStack = new MinStack();

minStack.push(-2);

minStack.push(0);

minStack.push(-3);

minStack.getMin(); --> Returns -3.

minStack.pop();

minStack.top(); --> Returns 0.

minStack.getMin(); --> Returns -2.

ans1.

class MinStack {
    stack<int> data;
    stack<int> helper;
public:
    MinStack() {
        
    }
    
    void push(int val) {
        data.push(val);
        if(helper.empty() || helper.top() >= val)
        {
            helper.push(val);
        }
    }
    
    void pop() {
        int top = data.top();
        data.pop();
        if(top == helper.top())
        {
            helper.pop();
        }
    }
    
    int top() {
         return data.top();
    }
    
    int getMin() {
        return helper.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();
 */

Ref:

https://github.com/azl397985856/leetcode/blob/master/problems/155.min-stack.md

https://blog.csdn.net/myRealization/article/details/106953583

https://www.cnblogs.com/grandyang/p/4091064.html

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LeetCode 155. Min Stack(Medium)#Stack

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