#include<iostream>
#include<algorithm>
#include<functional>
using namespace std;
void main(){
   int list[]={1,4,34,5},b[4];
   copy(a,a+4,ostream_iterator<int >(cout," "));
   cout<<endl;
   
   sort(a,a+4);
   copy(a,a+4,ostream_iterator<int >(cout, " "));
   cout<<endl;

   copy(a,a+4,b);
copy(b,b+4,ostream_iterator<int >(cout," "));
   cout<<endl;

   int *c=find(a,a+4,34);
   if(c=a+4) cout<<"没有这个数"<<endl;
      else   cout<<*c<<endl;
}

#include<algorithm>
#include<functional>
好神奇，都没有见过

运行了，程序提示错误，没有定义a呀？

STL