读一组整数到vector 对象，计算并输出每对相邻元素的和。如果读入元素个数 为奇数，则提示用户最后一个元素没有求和，并输出其值。

#include <iostream>
#include <string>
#include <vector>
using namespace std;
int main()
{
  vector<int> ivec;
  int ival;
  cout << "Enter numbers(Ctrl+Z to end):" << endl;
  while(cin >> ival)
  {
    ivec.push_back(ival);
  }//用cin读入一组整数并把它们存入一个vector对象中

  // 计算相邻元素的和并输出
  if (ivec.size() == 0) 
  {
    cout << "No element?!" << endl;
    return -1;
  }

  cout << "Sum of each pair of adjacent elements in the vector:"<< endl;

  for (vector<int>::size_type ix = 0; ix < ivec.size()-1;ix = ix + 2) 
  {
      cout << ivec[ix] + ivec[ix+1] << "\t";
      if ( (ix+1) % 6 == 0) // 每行输出6 个和
        cout << endl;
  }

  if (ivec.size() % 2 != 0) // 提示最后一个元素没有求和
  {
    cout << endl
    << "The last element is not been summed "
    << "and its value is "
    << ivec[ivec.size()-1] << endl;
  }

  return 0;
}