如果遍历map中最后一个元素rbegin(),end(),rend()

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#include "stdafx.h"


#include <iostream>
#include <map>
using namespace std;
int _tmain(int argc, _TCHAR* argv[])
{
        map<char,int> mymap;

        mymap['b'] = 100;
        mymap['a'] = 200;
        mymap['c'] = 300;
        map<char,int>::iterator it=mymap.begin();
        // show content:
        for (it; it!=mymap.end(); ++it)
                std::cout << it->first << " => " << it->second << '\n';
        //正确做法
         //输出map中的最后一个元素
        map<char,int>::reverse_iterator iter = mymap.rbegin(); //返回最后一个元素
        /*mymap.end();
        mymap.rend();
        */
        if (iter != mymap.rend())
        {
                std::cout << iter->first << " => " << iter->second << '\n';
        }

        //错误做法
         map<char,int>::iterator iter2 = mymap.end(); //
         //如果这样直接用会导致崩溃
         std::cout << iter2->first << " => " << iter2->second << '\n';
        if (iter2 != mymap.end())
        {
                std::cout << iter2->first << " => " << iter2->second << '\n';
        }

        /*mymap.end();
        mymap.rend();
        这两个函数只是标记找没找到 不是返回最后一个元素
        输出最后一个元素一定要切记
        Return iterator to end
        Returns an iterator referring to the past-the-end element in the map container.
        The past-the-end element is the theoretical element that would follow the last element in the map container.