使用unique_copy算法去除重复元素无效

#include <iostream>
#include <algorithm>
#include <list>
#include <vector>
#include <string>

using namespace std;

int main()
{
  list<string> sli;
  vector<string> svec;
  string word;
  
  cout<<"Enter strings for list:"<<endl;
  while(cin>>word)
    sli.push_back(word);
  
  unique_copy(sli.begin(),sli.end(),back_inserter(svec));

  cout<<"Vector:"<<endl;
  for(vector<string>::iterator iter=svec.begin();iter!=svec.end();++iter)
    cout<<*iter<<" ";
  cout<<endl;

  return 0;
}