剑指Offer系列---(23)包含min函数的栈

来源：互联网发布：mac ie浏览器编辑：程序博客网时间：2024/05/16 15:59

1.题目描述：
定义栈的数据结构，请在该类型中实现一个能够得到栈的最小元素的min函数。在该栈中，调用min、push及pop的时间复杂度都是O(1)。
2.分析：
实现方法：把每次的最小元素（之前的最小元素和新压入栈的元素两者的较小值）都保存在一个辅助栈中。
3.源代码：

#include <iostream>using namespace std;class CStackElement{public:    CStackElement(void){}    CStackElement(int data,int min=0)    {        m_nData = data;        m_nMin = min;    }        ~CStackElement(void){}    public:    int m_nData;    int m_nMin;};class CStack{public:    CStack(int maxSize);//普通构造函数，构造一个大小为maxSize的栈    CStack(const CStack &stack);//拷贝构造函数    CStack & operator=(const CStack &stack);//赋值函数    ~CStack(void);        void Push(int nPushElement);//向栈中压入一个元素nElement    void Pop();//从栈中弹出一个元素，并返回    int Min();//O(1)的时间返回最小元素值    private:    CStackElement *m_pStackArr;    int m_top;//指向栈顶元素的下一个位置    int m_nMaxSize;};//普通构造函数，构造一个大小为maxSize的栈CStack::CStack(int maxSize){    m_top = 0;//指向栈顶元素的下一个位置    m_nMaxSize = maxSize;    m_pStackArr = new CStackElement[m_nMaxSize];}//拷贝构造函数CStack::CStack(const CStack &stack){    m_top = stack.m_top;    m_nMaxSize = stack.m_nMaxSize;    m_pStackArr = new CStackElement[m_nMaxSize];    memcpy(m_pStackArr,stack.m_pStackArr,m_nMaxSize);}//赋值函数CStack & CStack::operator=(const CStack &stack){    if(this == &stack)//自赋值检查    {        return *this;    }    if(stack.m_top != 0)    {        if(m_nMaxSize <stack.m_nMaxSize)        {            m_nMaxSize = stack.m_nMaxSize;            delete[] m_pStackArr;            m_pStackArr = new CStackElement[m_nMaxSize];            memcpy(m_pStackArr, stack.m_pStackArr, m_nMaxSize);        }    }    return *this;}//向栈中压入一个元素nElementvoid CStack::Push(int nPushElement){    if(m_top == m_nMaxSize)    {        cout<<"栈满!"<<endl;    }    else if(m_top == 0)//栈空    {        m_pStackArr[m_top++].m_nData = nPushElement;        m_pStackArr[m_top++].m_nMin = nPushElement;        cout<<"压入"<<nPushElement<<endl;    }    else    {        if(m_pStackArr[m_top-1].m_nMin > nPushElement)        {            m_pStackArr[m_top].m_nMin = nPushElement;        }        else        {            m_pStackArr[m_top].m_nMin = m_pStackArr[m_top-1].m_nMin;        }        m_pStackArr[m_top++].m_nData = nPushElement;        cout<<"压入"<<nPushElement<<endl;    }}//从栈中弹出一个元素并返回void CStack::Pop(){    int nPopElement = 0;    if(m_top == 0)    {        nPopElement = -1;        cout<<"栈空!"<<endl;    }    else    {        nPopElement = m_pStackArr[--m_top].m_nData;        cout<<"弹出"<<nPopElement<<endl;    }}//O(1)的时间返回最小元素值int CStack::Min(){    if(m_top == 0)    {        cout<<"栈空!"<<endl;        return -1;    }    else    {        return m_pStackArr[m_top-1].m_nMin;    }}CStack::~CStack(void){    }int main(int argc,char *argv[]){        CStack stack(20);    stack.Push(4);    cout<<"Min:"<<stack.Min()<<endl;        stack.Push(5);    cout<<"Min:"<<stack.Min()<<endl;        stack.Push(2);    cout<<"Min:"<<stack.Min()<<endl;        stack.Pop();    cout<<"Min:"<<stack.Min()<<endl;        stack.Push(3);    cout<<"Min:"<<stack.Min()<<endl;}

4.运行效果：

压入4Min:4压入5Min:4压入2Min:2弹出2Min:4压入3Min:3Program ended with exit code: 0

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