#include?

const?int?MAX?=?50;
int?num[5];??//輸入的數
int?flag[10];??//是否已經用過
int?oper[5];??//1--‘+‘?2--‘-‘?3--‘*‘?4--‘/‘
int?n?m;?
int?p[10];??//臨時數組
int?bestp[10];??//最優數組
int?bestop[10];?//最優操作符
char?op[]?=?{‘?‘?‘+‘?‘-‘?‘*‘?‘/‘};
int?k;??//搜索深度逐漸加深

bool?found（）
{
????int?result?=?p[1];
????for（int?i=1;?i<=k;?i++）??//計算式子的結果
????{
????????switch（oper[i]）
????????{
????????case?1:
????????????result?+=?p[i+1];
????????????break;
????????case?2:
????????????result?-=?p[i+1];
????????????break;
????????case?3:
????????????result?*=?p[i+1];
????????????break;
????????case?4:
????????????result?/=?p[i+1];
????????????break;
????????}
????}

????return?result?==?m;
}

bool?backtrack（int?dep）
{
????if（dep?>?k+1）??//深度逐漸加深
????{
????????if（found（））
????????{
????????????//copy（p?p+n+1?bestp）;
???????????//?copy（oper?oper+n+1?bestop）;
????????????return?true;
????????}
????????else
????????????return?false;
????}

????for（int?j=1;?j<=n;?j++）?//可選的數字
????{
????????if（flag[j]?>?0）
????????????continue;
????????p[dep]?=?num[j];
????????flag[j]?=?1;
????????for（int?i=1;?i<=4;?i++）?//可選的操作符
????????{
????????????oper[dep]?=?i;
????????????if（backtrack（dep+1））
????????????????return?true;
????????????oper[dep]?=?0;
????????}
????????flag[j]?=?0;
????????p[dep]?=?0;
????}???
????return?false;