Codevs 1004 四子连棋

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<algorithm>
 5 using namespace std;
 6 #define Mod 9875321
 7 #define maxn 1000005
 8 long long read(){
 9     long long x=0,f=1;char ch=getchar();
10     while(ch<‘0‘||ch>‘9‘){
11         if(ch==‘-‘)f=-1;ch=getchar();
12     }
13     while(ch>=‘0‘&&ch<=‘9‘){
14         x=x*10+ch-‘0‘;ch=getchar();
15     }
16     return x*f;
17 }
18 int head=0,tail=2,ans=-1;
19 int step[maxn],xx[4]={0,0,1,-1},yy[4]={1,-1,0,0};
20 char q[maxn][5][5],a[5][5];
21 bool last[maxn],mp[maxn*10];
22 bool Valid(int x,int y,int t){
23     //该函数用于判断与空白格子交换的合法性
24     if(x>4||y>4||x<1||y<1||a[x][y]==‘O‘)return 0;
25     if(a[x][y]==‘B‘&&t==0)return 0;
26     if(a[x][y]==‘W‘&&t==1)return 0;
27     return 1;
28 }
29 bool equal(char a,char b,char c,char d){
30     if(a!=b || b!=c || c!=d)return 0;
31     return 1;
32 }
33 int gethash(char a[5][5]){
34     int t=0,key=0;
35     for(int i=1;i<=4;i++)
36       for(int j=1;j<=4;j++){
37           if(a[i][j]==‘O‘)t=0;
38           if(a[i][j]==‘W‘)t=1;
39           if(a[i][j]==‘B‘)t=2;
40           key=(key*3+t) % Mod;
41       }
42     return key;
43 }
44 bool check(char a[5][5]){
45     for(int i=1;i<=4;i++){
46         if(equal(a[i][1],a[i][2],a[i][3],a[i][4]))return 1;
47         if(equal(a[1][i],a[2][i],a[3][i],a[4][i]))return 1;
48     }
49     if(equal(a[1][1],a[2][2],a[3][3],a[4][4]))return 1;
50     if(equal(a[1][4],a[2][3],a[3][2],a[4][1]))return 1;
51     return 0;
52 }
53 void Move(int x,int y){
54     for(int k=0;k<4;k++){
55         int tx=x+xx[k],ty=y+yy[k];
56         if(!Valid(tx,ty,last[head]))continue;
57         
58         for(int i=1;i<=4;i++)
59           for(int j=1;j<=4;j++)
60             a[i][j]=q[head][i][j];
61             
62         swap(a[x][y],a[tx][ty]);
63         if(mp[gethash(a)])continue;
64         mp[gethash(a)]=1;
65         tail++;
66         for(int i=1;i<=4;i++)
67           for(int j=1;j<=4;j++)
68             q[tail][i][j]=a[i][j];
69         
70         step[tail]=step[head]+1;
71         last[tail]=last[head]^1;
72         if(check(a))ans=step[tail];
73     }
74 }
75 void BFS(){
76     while(head != tail){
77         for(int i=1;i<=4;i++)
78           for(int j=1;j<=4;j++)
79             if(q[head][i][j]==‘O‘)
80               Move(i,j);
81         if(ans != -1) return;
82         head++;
83     }
84 }
85 int main()
86 {
87     for(int i=1;i<=4;i++)
88       scanf("%s",a[i]+1);
89     for(int i=1;i<=4;i++)
90       for(int j=1;j<=4;j++)
91         q[0][i][j]=q[1][i][j]=a[i][j];
92         
93     last[0]=0;last[1]=1;
94     BFS();
95     printf("%d\n",ans);
96     return 0;
97 }