SGU 289. Challenging Tic-Tac-Toe

注意一个问题就是不合法状态的判定。一个是点数不对，一个是X赢了，但是0接着下了一个子，一个是0赢了，但X也接着下了子，判断一下就行了。

做法是直接搜索，然后调参数。。。比较难懂的说。

 #include <bits/stdc++.h>
 #define rep(_i, _n) for(int _i = 1; _i <= _n; ++_i)
 char gchar() {
     char ret = getchar();
     for(; ret == '\n' || ret == '\r' || ret == ' '; ret = getchar());
     return ret;
 }
 typedef long long LL;
 typedef double    DB;
 const int maxn = 0x3f3f3f3f;
 using namespace std;
 int ch[];

 bool win(int *t, int player) {
     for(int i = ; i < ; ++i) {
         if(t[i * ] == player && t[i *  + ] == player && t[i *  + ] == player)
             return true;
         if(t[i] == player && t[i + ] == player && t[i + ] == player)
             return true;
     }
     if(t[] == player && t[] == player && t[] == player) return true;
     if(t[] == player && t[] == player && t[] == player) return true;
     return false;
 }

 void dfs(int player, int &result) {
     if(win(ch, result ^ )) {
     //    result ^= 1;
         return ;
     }
     else if(player == ) result = ;
     int cnt_win_state = , cnt_draw_state = ;
     for(int i = ; i < ; ++i) {
         if(ch[i] == ) {
             ch[i] = (player & ) ^ ;
             int tmp = result ^ ;
             dfs(player + , tmp);
             if(tmp == (result ^ )) ++cnt_win_state;
             if(tmp == ) ++cnt_draw_state;
             ch[i] = ;
         }
     }
     if(cnt_win_state > ) result = result ^ ;
     else if(cnt_draw_state > ) result = ;
 }

 int main() {
 #ifndef ONLINE_JUDGE
     freopen("chess.in", "r", stdin), freopen("chess.out", "w", stdout);
 #endif

     for(; ;) {
         char c = gchar();
         if(c == 'Q') break;
         if(c == '') ch[] = ;
         else if(c == 'X') ch[] = ;
         else ch[] = ;
         for(int i = ; i <= ; ++i) {
             c = gchar();
             if(c == 'Q') break;
             if(c == '') ch[i] = ;
             else if(c == 'X') ch[i] = ;
             else ch[i] = ;
         }
         int cnt1 = , cnt2 = ;
         for(int i = ; i < ; ++i)
             if(ch[i] == ) ++cnt1;
             else if(ch[i] == ) ++cnt2;
     //    for(int i = 0; i < 9; ++i) printf("%d ", ch[i]);
     //    puts("");
     //    printf("%d %d\n", cnt1, cnt2);
         if(!(cnt1 - cnt2 ==  || cnt1 - cnt2 == ) || (win(ch, ) && win(ch, )) || (win(ch, ) && cnt1 > cnt2) || (win(ch, ) && cnt1 == cnt2)) {
             printf("Illegal position.\n");
         } else {
             int result = ((cnt1 + cnt2) & ) ^ ;
             dfs(cnt1 + cnt2, result);
             if(result == ) printf("Game is a draw.\n");
             else if(result == ) printf("X wins.\n");
             else printf("0 wins.\n");
         }
     }
     return ;
 }