练习3.24

/*************************************************************************    > File Name: 3_24.cpp    > Author:     > Mail:     > Created Time: Sun 09 Apr 2017 08:26:47 PM CST ************************************************************************/#include<iostream>#include<vector>using namespace std;int main(){    vector<int> ivec;    int n;    cin>>n;    for(int i = 0; i < n; ++i)// input num by function i*i-5    {        ivec.push_back(i * i - 5);        cout<<i * i - 5<<" ";    }    cout<<endl<<endl;    for(auto it = ivec.cbegin(); it != ivec.cend() - 1;)     {        cout<<(*it) + (*(++it))<<" ";    }    cout<<endl<<endl;    for(auto it_beg = ivec.cbegin(), it_end = ivec.cend() - 1; ; ++it_beg, --it_end)    {        if(it_beg < it_end)            cout<<*it_beg + *it_end<<" ";        else if(it_beg == it_end)            cout<<*it_beg + *it_end<<" ";        else             break;    }    cout<<endl;    return 0;}