MAP使用方法

一、map的说明
  1 头文件
  #include <map>
  
  2 定义
  map<string, int> my_Map;
  或者是typedef map<string, int> MY_MAP;
  MY_MAP my_Map;
  
  3 插入数据
  (1) my_Map["a"] = 1;
  (2) my_Map.insert(map<string, int>::value_type("b",2));
  (3) my_Map.insert(pair<string,int>("c",3));
  (4) my_Map.insert(make_pair("d",4));
  
  4 查找数据和修改数据
  (1) int i = my_Map["a"];
            my_Map["a"] = i;
  (2) MY_MAP::iterator my_Itr;
            my_Itr.find("b");
            int j = my_Itr->second;
            my_Itr->second = j;
  不过注意，键本身是不能被修改的，除非删除。
  
  5 删除数据
  (1) my_Map.erase(my_Itr);
  (2) my_Map.erase("c");
  还是注意，第一种情况在迭代期间是不能被删除的，道理和foreach时不能删除元素一样。
  
  6 迭代数据
  for (my_Itr=my_Map.begin(); my_Itr!=my_Map.end(); ++my_Itr) {}
  
  7 其它方法
  my_Map.size() 返回元素数目
  my_Map.empty() 判断是否为空
  my_Map.clear() 清空所有元素
  可以直接进行赋值和比较：=, >, >=, <, <=, != 等等
  
  更高级的应用查帮助去吧，^_^;

二\map的举例

要求: 将mymap中itemstruct 的a大于100的项删除
struct itemstruct
  {
            int a;
            char b[20];
  };
  map<string, itemstruct > mymap.
  
解答1:
  #include <iostream>
  #include <ctime>
  #include <map>
  using namespace std;
  typedef struct itemstruct
  {
            int a;
            char b[20];
  }itemS;
  itemS s[4] = {{102,"what"},
                          {33, "hello"},
                          {198,"world"},
                          {45, "c++"}
                      };;
  
  
  int main()
  {
            map<string, itemS> mymap;
            string str[4] = {"1st","2nd","3rd","4th"};
            for(int i = 0; i<4; i++)
            {
                 mymap.insert(make_pair(str[i], s[i]));
            }
            
            map<string,itemS>::iterator it;
            for(it=mymap.begin(); it!=mymap.end(); it++)
            {
               if(it->second.a >100){
                  i=mymap.erase(it); ----->正确
    mymap.erase(it); ----->it失效..
        }
            }
  //first是Key, second是value;
            for(it = mymap.begin(); it!=mymap.end(); it++)
            {
                          cout<<it->first<<" "<<it->second.a<<" "<<it->second.b<<endl;
            }
          system("pause");
          return 0;
  }

解答2：
#include<map>
  #include<iterator>
  #include<string>
  #include<iostream>
  #include<cstring>
  using namespace std;
  struct itemstruct
  {
            int a;
            char b[20];
            itemstruct(int t,char*str)
    {
    a=t;
    strcpy(b,str);
    }
  };
  int main()
  {
  map<string,itemstruct>mymap;
  mymap.insert(make_pair("a",itemstruct(10,"hanzhou")));
  mymap.insert(make_pair("ab",itemstruct(20,"fuzhou")));
  mymap.insert(make_pair("abc",itemstruct(30,"zhengzhou")));
  mymap.insert(make_pair("abcd",itemstruct(200,"wuhan")));
  mymap.insert(make_pair("abcde",itemstruct(150,"kunming")));
  mymap.insert(make_pair("abcdef",itemstruct(50,"xiamen")));
  map<string,itemstruct>::iterator it=mymap.begin();
  while(it!=mymap.end())
  {
  if((it->second).a>100)mymap.erase(it++);
  else it++;
  }
  it=mymap.begin();
  while(it!=mymap.end())
  {
  cout<<it->first<<" "<<(it->second).a<<" "<<(it->second).b<<endl;
  it++;
  }
  system("PAUSE");
  return 0;
  }

解答3：
  for(map<string, itemstruct>::iterator i = mymap.begin(); i != mymap.end();)
  {
          if(i->second.a > 100)
                  i = mymap.erase(i);
          else
                  ++i;
  }

解答4: VC6中编译map编译出错的解决方法
Warnings similar to the following are generated even if you use the warning pragma to disable the warning: warning C4786: 'std::rb_tree<CAiSpanningTree<State,std::less<State>>::TransClosureNode, CAiSpanningTree<State,std::less<State>>::TransClosureNode,std::ident<Cai SpanningTree<State,std::less<State>>::TransClosureNode,CAiSpanningTree<S tate,std::less<State>>::TransClosureNode>,std::less<CAiSpanningTree<Stat e,std::less<State>>::TransClosureNode>>' : identifier was truncated to '255' characters in the debug information


解决code 加在stdafx.h的头文件处:

   #pragma warning(disable:4786)