C++ :

#include<cstdio>
#include<iostream>
#include<cstdlib>
using  namespace std;
int  book[6],c;
bool flag[6],like[6][6]={{0,0,0,0,0,0},{0,0,0,1,1,0},{0,1,1,0,0,1},
                                    {0,0,1,1,0,0},{0,0,0,0,1,0},{0,0,1,0,0,1}};;
char s[5][20]={"Student Zhang","Student Wang","Student Liu","Student Sun","Student Li"};
int  search(int);
int  print();
int  main()
{
  for (int i=1;i<=5;i=i+1) flag[i]=1;
  search(1);                                    //从第1个开始选书，递归。
  return 0;
} 
int search(int i)                              //递归函数 
{
  for (int j=1;j<=5; j++)                   //每个人都有5本书可选
  if (flag[j]&&like[i][j])                      //满足分书的条件
  {
    flag[j]=0;                                    //把被选中的书放入集合flag中，避免重复被选
    book[i]=j;                                   //保存第i个人选中的第j本书
    if (i==5) print();                          //i=5时，所有的人都分到书，输出结果
       else search(i+1);                    //i<5时，继续递归分书
    flag[j]=1;                                    //回溯：把选中的书放回，产生其他分书的方案
    book[i]=0;
  }
  return 0;
}  

int print()
{
  c=c+1;                                                                //方案数累加1
  cout <<"answer " <<c <<":\n";  
  for (int i=1;i<=5;i=i+1)
    cout <<s[i-1]<<":" <<char(64+book[i]) <<endl;  //输出分书的方案
	return 0;
}