自定义函数使用map排序

#pragma warning(disable:4786)
#include <iostream>
#include <string>
#include <map>
#include <algorithm>
using namespace std;

/* 从小到大排序 */
struct ltstr
{
     bool operator()(const char* s1, const char* s2) const
  {
        return strcmp(s1, s2) < 0;
     }
};
typedef map<const char*, int,ltstr> MYDATAMAP;
typedef MYDATAMAP::iterator Itermydata;

int main(int argc, char* argv[])
{
 MYDATAMAP mydata;
 mydata.insert(Itermydata::value_type("3",9));
 mydata.insert(Itermydata::value_type("4",9));
 mydata.insert(Itermydata::value_type("1",9));
 mydata.insert(Itermydata::value_type("2",9));
 Itermydata begin = mydata.begin();
 for(; begin != mydata.end(); ++begin)
 {
  cout<<"Key: " << begin->first
   <<"   Value: " << begin->second <<endl;
 }
    mydata.clear();
 return 0;
} 

结果输出为:

Key: 1     Value: 9

Key: 2     Value: 9

Key: 3     Value: 9

Key: 4     Value: 9