155. Min Stack

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

Implement the MinStack class:

  • MinStack() initializes the stack object.
  • void push(int val) pushes the element val onto the stack.
  • void pop() removes the element on the top of the stack.
  • int top() gets the top element of the stack.
  • int getMin() retrieves the minimum element in the stack.

分别将数据保存在一个Priority Queue和一个栈中。
pop方法pop掉stack的内容,然后将其从优先队列中移除。
top方法返回stack的栈顶。
getMin方法返回优先队列的顶。

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class MinStack {
Queue<Integer> pq;
Stack<Integer> stack;
public MinStack() {
pq = new PriorityQueue<>();
stack = new Stack<>();
}

public void push(int val) {
pq.add(val);
stack.add(val);
}

public void pop() {
int i = stack.pop();
pq.remove(i);

}

public int top() {
return stack.peek();
}

public int getMin() {
return pq.peek();
}
}

/**
* 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();
*/
Author

Xander

Posted on

2022-04-30

Updated on

2022-04-29

Licensed under

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