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56 lines (50 loc) · 1.19 KB
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package com.algorithdemo.stack;
import java.util.Stack;
/**
* 一个有getMin功能的栈
* 题目描述：实现一个特殊的栈，在栈的基本功能上，再实现返回栈中最小元素的操作
*/
public class MyStack {
private Stack<Integer> stackData;
private Stack<Integer> stackMin;
public MyStack(){
this.stackData = new Stack<Integer>();
this.stackMin = new Stack<Integer>();
}
/**
* 入栈
* @param num
*/
public void push(int num) {
if(stackMin.isEmpty()){
this.stackData.push(num);
}else if(num <= this.getMin()){
this.stackMin.push(num);
}
this.stackData.push(num);
}
/**
* 出栈
* @return
*/
public int pop(){
if(this.stackData.isEmpty()){
throw new RuntimeException("Your stack is empty.");
}
int value = this.stackData.pop();
if(value==this.getMin()){
this.stackMin.pop();
}
return value;
}
/**
* 返回栈的最小元素
* @return
*/
public int getMin(){
if(this.stackMin.isEmpty()){
throw new RuntimeException("Your stack is empty.");
}
return this.stackMin.peek();
}
}