set容器

set用来保存只有键值没有实值的容器，这类容器的基础结构是红黑树，这个红黑树各节点数据是单一数据而不是pair。当元素插入容器时，会按照指定排序自动排序，默认从小到大。

#include<iostream>#include<set>using namespace std;int main(){    set<int> set1;    set<int>::iterator it;    for(int i=0;i<5;i++){        set1.insert(i*10);    }    pair<set<int>::iterator,bool>ret=set1.insert(20);    if(!ret.second){        it=ret.first;        cout<<*ret.first<<endl;    }    int insGrup[]={5,10,15};    set1.insert(insGrup,insGrup+3);    for(it=set1.begin();it!=set1.end();it++){        cout<<*it<<" ";     }    cout<<endl;    set1.erase(24);    for(it=set1.begin();it!=set1.end();it++){        cout<<*it<<" ";    }    it=set1.begin();    set1.erase(it);    for(it=set1.begin();it!=set1.end();it++){        cout<<*it<<" ";    }    set1.erase(it,set1.end());    for(it=set1.begin();it!=set1.end();it++){        cout<<*it<<" ";    }    set1.clear();    if(set1.empty()){        cout<<"\nset1 is empty"<<endl;    }    if(set1.size()==0){        cout<<"set1 size is 0"<<endl;    }    int array[]={24,12,18,9};    set<int>first(array,array+2),second(array+1,array+4);    first.swap(second);    for(it=first.begin();it!=first.end();it++){        cout<<*it<<" ";    }     cout<<endl;    for(it=second.begin();it!=second.end();it++){        cout<<*it<<" ";    }    cout<<endl;    return 0;}