C++ primer P81 练习3.5

#include <iostream>
#include <string>
using namespace std;
int main(){
   string s,s1,s2;
   int i = 0;
   string str[100];
   while (cin >> s){
      str[i] = s;
      cout << s << endl;
      i++;
    }
   int j;
   for (j = 0; j <= i;j++){
      s1 = s1 + str[j];
      s2 = s2 + str[j]+" ";
   }
   cout << s1 << endl<<s2<<endl;
   return 0;
}