第2题:设计包含min函数的栈
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第2题:定义栈的数据结构,要求添加一个min函数,能够得到栈的最小元素
要求:函数min、push、pop的时间复杂度都是O(1)
新元素入栈时,将包括自身在内的所有元素中的最小值保存在自身节点的minData中,这样不管出栈/入栈,栈顶都将永远保存当前所有元素的最小值。
package test002;
/**
* Created by cq on 2015/3/25.
* 节点node的定义
*/
public class Node {
private int data;
private int minData;
private Node next;
public Node(int data){
this.data = data;
this.next = null;
this.minData = data;
}
public int getData() {
return data;
}
public void setData(int data) {
this.data = data;
}
public Node getNext() {
return next;
}
public void setNext(Node next) {
this.next = next;
}
public int getMinData() {
return minData;
}
public void setMinData(int minData) {
this.minData = minData;
}
}
package test002;
/**
* Created by cq on 2015/3/25.
* 第二题:定义栈的数据结构,要求添加一个min函数,能够得到栈的最小元素
* 要求:函数min、push以及pop的时间复杂度为O(1)
*/
public class MinStack {
private Node stack;
public MinStack(){
stack = null;
}
public boolean isEmpty(){
return stack == null;
}
//返回最小值,不对栈进行操作
public int getMinData(){
if (isEmpty()){
//用int型的最大值表示异常
return Integer.MAX_VALUE;
}
return stack.getMinData();
}
public int pop(){
if (isEmpty()){
return Integer.MAX_VALUE;
}
int temp = stack.getData();
stack = stack.getNext();
return temp;
}
public void push(int data){
Node node = new Node(data);
if (!isEmpty()){
if (node.getMinData() > stack.getMinData()){
node.setMinData(stack.getMinData());
}
node.setNext(stack);
}
stack = node;
}
public static void main(String[] args){
MinStack minStack = new MinStack();
minStack.push(5);
System.out.println(minStack.getMinData());
minStack.push(9);
System.out.println(minStack.getMinData());
minStack.push(4);
System.out.println(minStack.getMinData());
minStack.push(3);
System.out.println(minStack.getMinData());
minStack.push(1);
System.out.println(minStack.getMinData());
minStack.pop();
System.out.println(minStack.getMinData());
minStack.pop();
System.out.println(minStack.getMinData());
minStack.pop();
System.out.println(minStack.getMinData());
}
}
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http://www.cnblogs.com/read-the-spring-and-autumn-annals-in-night/