c++中stl----map

1 map的本质

(1)关联式容器，键值对应

(2)增加和删除节点对迭代器的影响很小。

(3)对于迭代器来说不可以修改键值，只能修改对应的实值。

(4)map内部数据的祖居是自建一颗红黑树(或者说是平衡二叉树)，具有自动排序的功能。

2 map的查增删

(1)map的插入

 1 #include <map>
 2 #include <string>
 3 #include <iostream>
 4 using namespace std;
 5 
 6 int main()
 7 {
 8     //方式一 pair
 9     map<int,string> mapStudent;
10     mapStudent.insert(pair<int,string>(1,"lan"));
11     mapStudent.insert(pair<int,string>(2,"ji"));
12     mapStudent.insert(pair<int,string>(1,"kjh"));
13     map<int,string>::iterator iter;
14     map<int,string>::iterator iter1;
15     //方式二
16     map<int string> mapStudent1;
17     mapStudent1.insert(map<int,string>::value_type(1,"nihao"));
18     mapStudent1.insert(map<int,string>::value_type(1,"ben"));
19     for(iter=mapStudent.begin();iter!=mapStudent.end();iter++)
20     {
21         cout<<iter->first<<" "<<iter->second<<endl;
22     }
23     for(iter=mapStudent1.begin();iter!=mapStudent1.end();iter++)
24     {
25         cout<<iter->first<<" "<<iter->second<<endl;
26 
27     }
28     return 0;     
29 }

View Code

2 map的遍历

 1 #include <map>
 2 #include <string>
 3 #include <iostream>
 4 using namespace std;
 5 
 6 int main()
 7 {
 8     map<int,string> mapStudent;
 9     mapStudent[1]="stu_one";
10     mapStudent[1]="stu_two";
11     mapStudent[1]="stu_three";
12     map<int,string>::iterator iter = mapStudent.find(1);
13     if(iter!=mapStudent.end())
14     {
15         cout<<"找到了 value="<<iter->second<<endl;
16     }else
17     {
18         cout<<"没有找到"<<endl;
19     }
20     return 0;
21 }

View Code

3 map的删除

 1 #include <map>
 2 #include <string>
 3 #include <iostream>
 4 using namespace std;
 5 
 6 int main()
 7 {
 8     map<int,string> mapStudent;
 9     mapStudent[1]="stu_one";
10     mapStudent[1]="stu_two";
11     mapStudent[1]="stu_three";
12     map<int,string>::iterator iter = mapStudent.begin();
13     for(;iter!=mapStudent.end();)
14     {
15         if((*iter).sencond=="stu_one")
16         {
17             mapStudent.erase(iter++);//iter被erase以后就会失效 所以后面不能再有iter++
18         }else
19         {
20             ++iter;
21         }
22     }
23     for(iter=mapStudent1.begin();iter!=mapStudent1.end();iter++)
24     {
25         cout<<iter->first<<" "<<iter->second<<endl;
26 
27     }
28     return 0;
29 }

View Code

4 map排序

默认按照key从小到大。从大到小greater 相反less

 1 #include <map>
 2 #include <string>
 3 #include <iostream>
 4 using namespace std;
 5 int main()
 6 {
 7     map<string,int,greater<string>> mapStudent;
 8     mapStudent['nisan']=90;
 9     mapStudent['nisan']=70;
10     mapStudent['nisan']=80;
11     map<string,int>::iterator iter = mapStudent.begin();
12     for(iter=mapStudent.begin();iter!=mapStudent.end();iter++)
13     {
14         cout<<iter->first<<" "<<iter->second<<endl;
15     }
16     return 0;
17 }

View Code

自定义排序方式

 1 #include <string>
 2 #include <iostream>
 3 using namespace std;
 4 struct CmpByKeyLength
 5 {
 6     bool operator()(const string &k1,const string&k2){
 7         return k1.length()<k2.length();
 8     }
 9 };
10 int main()
11 {
12     map<string,int,CmpByKeyLength>mapStudent;
13     mapStudent['nisan']=90;
14     mapStudent['nisan']=70;
15     mapStudent['nisan']=80;
16     map<string,int>::iterator iter = mapStudent.begin();
17     for(iter=mapStudent.begin();iter!=mapStudent.end();iter++)
18     {
19         cout<<iter->first<<" "<<iter->second<<endl;
20     }
21     return 0;
22 }

View Code

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