C++中map容器的说明和使用技巧
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<string,int>("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)
