C++ STL模板

　　Ｃ++中的STL(Standard Template Library)用起来挺方便的，这里我们来做一下总结。

一、set

　　set是STL中一种标准关联容器 （vector,list,string,deque都是序列容器，而set，multiset，map，multimap是标准关联容器），它底层使用 平衡的搜索树——红黑树实现，插入删除操作时仅仅需要指针操作节点即可完成，不涉及到内存移动和拷贝，所以效率比较高。

　　在set中元素都是唯一的，而且默认情况下会对元素 自动进行升序排列，支持集合的交(set_intersection),差(set_difference) 并(set_union)，对称差(set_symmetric_difference) 等一些集合上的操作，如果需要集合中的元素允许重复那么可以使用multiset。

　　1）插入(insert)

　　set的元素添加时使用insert()方法，示例如下：

 #include<bits/stdc++.h>
 using namespace std;

 int main(){
     set<int>s;
     int n;
     cout << "input: ";
     for(int i = ; i < ; i++){
         cin >> n;
         s.insert(n);
     }
     cout << "output: ";
     for(set<int>::iterator it = s.begin(); it != s.end(); ++it){
         cout << *it << ' ';
     }
 }

　　运行结果如下：

　　aaarticlea/png;base64,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" alt="" />

　　可见set已为我们剔除了相同的元素了，并且默认升序输出。假如我们想构造一个升序的set，可以这样声明：set<int, greater<int>> s ;

　　2）历遍

　　set的历遍一般是用迭代器iterator，这是对指针的封装，示例代码如上。

　　3）初始化

　　我们可以使用数组来进行初始化，或者用复制构造函数：

 int main(){
     int A[] = {, , };
     set<int> setA(A, A + );
     set<int> setB(setA);
 }

4）并集、交集、差集

　　利用set的方法可以方便地求出并集、交集和差集：　

 #include<bits/stdc++.h>
 using namespace std;

 int main(){
     int A[] = {, , };
     int B[] = {, , , -};
     set<int> setA(A, A + );
     set<int> setB(B, B + );
     set<int> set1, set2, set3;

     set_union(setA.begin(), setA.end(), setB.begin(), setB.end(), insert_iterator<set<int>>(set1, set1.begin()));
     set_intersection(setA.begin(), setA.end(), setB.begin(), setB.end(), insert_iterator<set<int>>(set2, set2.begin()));
     set_difference(setA.begin(), setA.end(), setB.begin(), setB.end(), insert_iterator<set<int>>(set3, set3.begin()));

     cout << "union: ";
     for(set<int>::iterator it = set1.begin(); it != set1.end(); ++it) cout << *it << ' '; cout << endl;

     cout << "intersection: ";
     for(set<int>::iterator it = set2.begin(); it != set2.end(); ++it) cout << *it << ' '; cout << endl;

     cout << "difference: ";
     for(set<int>::iterator it = set3.begin(); it != set3.end(); ++it) cout << *it << ' '; cout << endl;
 }

　　三个函数的参数都类似，运行效果如下：

　　aaarticlea/png;base64,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" alt="" />

二、map

　　map是STL的一个关联容器，它提供一对一（其中第一个可以称为关键字，每个关键字只能在map中出现一次，第二个可能称为该关键字的值）的数据处理能 力，由于这个特性，它完成有可能在我们处理一对一数据的时候，在编程上提供快速通道。这里说下map内部数据的组织，map内部自建一颗红黑树(一种非严 格意义上的平衡二叉树)，这颗树具有对数据自动排序的功能，所以在map内部所有的数据都是有序的。

　　1）声明

1     map<string, int> m1;
     map<int, string> m2;
     map<string, char> m3;
     map< char, string> m4;
     map<char, int> m5;
     map<int, char> m6;

　　　以上我们分别声明了6个不同的映射。　

　　2）插入

 #include<bits/stdc++.h>
 using namespace std;

 int main(){
     map<string, string> m;

     m.insert(make_pair("A", "apple"));
     m.insert(pair<string, string>("B", "banana"));
     m.insert(map<string, string>::value_type("C", "cherry"));
 }      

　　以上我们分别用了三种方式进行元素的插入，其效果都是一样的。当然还有另一种简单的方式如：m["A"] = "apple"。这种方式有所不同：一般的话，后面的方式可以修改前面的方式的值，反之不能。

 #include<bits/stdc++.h>
 using namespace std;

 int main(){
     map<string, string> m;
     //m["A"] = "foo";
     m.insert(make_pair("A", "apple"));
     m.insert(pair<string, string>("B", "banana"));
     m.insert(map<string, string>::value_type("C", "cherry"));
     m["A"] = "boo";

     cout << m["A"] << endl;
     cout << m["B"] << endl;
     cout << m["C"] << endl;
 } 

　　上面我们用m["A"] = "boo" 来修改原来的映射，运行结果如下：

　　aaarticlea/png;base64,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" alt="" />

　　可见修改成功。

 #include<bits/stdc++.h>
 using namespace std;

 int main(){
     map<string, string> m;
     m["A"] = "foo";
     m.insert(make_pair("A", "apple"));
     m.insert(pair<string, string>("B", "banana"));
     m.insert(map<string, string>::value_type("C", "cherry"));
     //m["A"] = "boo";

     cout << m["A"] << endl;
     cout << m["B"] << endl;
     cout << m["C"] << endl;
 }      

　　现在我们用make_pair试图进行修改，结果如下：

　　aaarticlea/png;base64,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" alt="" />

　　可见，修改失败。

　　3）历遍

 #include<bits/stdc++.h>
 using namespace std;

 int main(){
     map<string, string> m;

     m.insert(make_pair("A", "apple"));
     m.insert(pair<string, string>("B", "banana"));
     m.insert(map<string, string>::value_type("C", "cherry"));

     for(map<string, string>::iterator it = m.begin(); it != m.end(); ++it){
         cout << it->first << ' ' << it->second << endl;
     }

     cout << m["A"] << endl;
     cout << m["B"] << endl;
     cout << m["C"] << endl;

 }      

　　我们可以使用map的迭代器进行历遍，分别输出first和second，也可以像使用数组一样对map进行访问，运行结果如下：

　　 aaarticlea/png;base64,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" alt="" />

　　4）删除

　　在刚在的代码中，我们需要删除元素，可以这么做：

     map<string, string>::iterator it;
     it = m.find("A");
     m.erase(it);

　　5）查找

　　假如我们想要知道一个映射是否存在，可以这么做：

     map<int, char> m;
     if(m.find() == m.end()) cout << "not found" << endl;
     else cout << "found" << endl;

　　假若m[0]未被赋值，则m.find(0) == m.end()。

　　//End