C++Primer _vector _习题3.13

#include <iostream>#include <vector>using namespace std;int main(){vector<int> vi;int a;while (cin>>a){vi.push_back(a);}if (vi.size()==0){cout<<"没有元素"<<endl;return -1;}for (vector<int>::size_type first=0,last=vi.size()-1;first<=last;first++,last--){if (first==last)cout<<"没有求和的元素"<<vi[first];elsecout<<vi[first]+vi[last]<<endl;}return 0;}