set 容器

//set 容器里面不可以有重复的元素//a 和 b 重复 == “a必须排在b前面” 和 “b必须排在前面”都不成立#include<iostream>#include<cstring>#include<set>using namespace std;int main(){    set<int> st;    int a[10]={1,2,3,8,7,7,5,6,8,12};    for(int i = 0; i < 10; ++i)        st.insert(a[i]);    cout << st.size() <<endl;    set<int>::iterator i;    for(i = st.begin(); i != st.end(); ++i)        cout << *i << " ";        cout << endl;    //输出： 1,2,3,5,6,7,8,12    //插入数据    pair< set<int>::iterator, bool >result = st.insert(2);    if( ! result.second )        cout << *result.first << " already exists.";    else        cout << *result.first << " inserted." << endl;    return 0;}/*pair< set<int>::iterator, bool>相当于struct{    set<int>::iterator first;    bool second;};*/