c++ map 插入数据后，begin(),end()以及当前迭代器的变化

#include <map>
#include <string>
#include <stdio.h>
#include <iostream>

using namespace std;
#define NUM 6
string string_trim(const string &data,const char *space){
    size_t begin_pos = data.find_first_not_of(space);
    size_t end_pos = data.find_last_not_of(space);
    if(begin_pos != string::npos)
    {
        return data.substr(begin_pos,end_pos-begin_pos+1);
    }
    return string("");
}
int main()
{
    map<int, int> myMap;
    for(int i=1; i<NUM; ++i)
    {
        myMap.insert(pair<int, int>(i*1000,i*100));
    }
/*
    for(int i=0; i<NUM; ++i)
        {
                myMap.insert(pair<int, int>(i,i*10000));
        }
*/
    int n = 8;    
    map<int, int>::iterator iter = myMap.begin();
    map<int, int>::iterator iterEnd = myMap.end();//先保存iterEnd，用于比较myMap.end()是否会发生变化
    map<int, int>::iterator iterBegin = iter;
    //printf("minux=%d\n",iterEnd-iter);
    myMap.insert(pair<int, int>(100000,1));
    if(iterEnd== myMap.end())
    {
        printf("aaa not changed end()\n");
    }
    for(; iter!=myMap.end(); ++iter)
    {
        bool beginEqual = iter==iterBegin;
        bool endEqual = (iter== iterEnd);
        printf("key:%d, value:%d\n", iter->first, iter->second);
//        printf("bgeinEqual = %d, endEqual = %d\n", beginEqual, endEqual);
        if( n<20) myMap.insert(pair<int, int>(n,n*10));
        ++n;
        //myMap.erase(iter);
    //    iterEnd = myMap.end();
        
//        printf("key:%d, value:%d\n", iter->first, iter->second);
    }
    if(iter==iterEnd)
    {
        printf("end not change\n");
    }
    else
    {
        printf("end is changed\n");
    }
    if(iterBegin == myMap.begin())
    {
        printf("begin not change\n");
    }
    else
    {
        printf("begin is changed\n");
    }
    printf("---遍历打印myMap里的内容-----------\n");
    iter = myMap.begin();
    for(; iter!=myMap.end(); ++iter)
    {
        printf("key:%d, value:%d\n", iter->first, iter->second);
                
    }
    printf("finished\n");
    return 0;
}