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【Leetcode】Min Stack

2024-08-06 02:31:30   228人阅读

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

这道题的关键就在于你要怎么存这些数。其实stack本身存就可以，但是需要考虑一个问题：加入我push1，3，5，4，0，当pop完0以后你需要回到让min等于1.所以我们在push0的时候应该先push1，再push0，这样pop0之后，我们再pop0之前的1赋给min就好了~~~~~~

import java.util.ArrayList;
import java.util.Stack;

class MinStack {
Stack<Integer> stack = new Stack<Integer>();
int min;

public static void main(String args[]){
MinStack ms  = new MinStack();
ms.push(0);
ms.push(1);
ms.push(0);
System.out.println(ms.getMin());
ms.pop();
//System.out.println(ms.pop(););
System.out.println(ms.getMin());
}

    public void push(int x) {
    
if(stack.empty()||x<=min){
    
stack.push(min);
    
stack.push(x);
    
min = x;
    
}
    
else stack.push(x);
    }

    public void pop() {
    
int tmp = stack.pop();
    
if(tmp==min)
min=stack.pop();
    }

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

    public int getMin() {
        return min;
    }
}


【Leetcode】Min Stack


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