代码如下：
dbfs：
1 #include <iostream>
2 #include <map>
3 #include <algorithm>
4 #include <string>
5 #include <queue>
6 using namespace std;
7 typedef long long LL;
8
9 int eight[3][3], xx, xy, dx[]={0,0,-1,1,0}, dy[]={0,1,0,0,-1};
10 char dir[] = "orudl";
11
12 LL encode(){
13 LL s=eight[2][2];
14 for(int i=7; i>=0; --i){
15 s <<=4;
16 s |= eight[i/3][i%3];
17 }
18 return s;
19 }
20 void decode(LL s){
21 for(int i=0; i<9; ++i){
22 eight[i/3][i%3] = s%16;
23 if(s%16 == 0)
24 xx = i/3, xy = i%3;
25 s >>=4;
26 }
27 }
28 void print_state(LL s){
29 printf("s:%d,xx,xy:", s);
30 decode(s);
31 printf("%d,%d\n",xx,xy);
32 for(int i=0; i<3; ++i){
33 for(int j=0; j<3; ++j)
34 printf("%d ", eight[i][j]);
35 printf("\n");
36 }
37
38 }
39 queue<LL> que[2];
40 map<LL,pair<int,LL> > mp[2];// pair:d,ps
41
42 void print(LL s){
43 int d = mp[0][s].first;
44 LL ts=s;
45 string ope;
46 while(d!=-1){
47 ope.push_back(dir[d]);
48 ts = mp[0][ts].second;
49 d = mp[0][ts].first;
50 }
51 reverse(ope.begin(), ope.end());
52 cout<< ope;
53 ope.clear(), d = mp[1][s].first, ts = s;
54 while(d!=-1){
55 ope.push_back(dir[d]);
56 ts = mp[1][ts].second;
57 d = mp[1][ts].first;
58 }
59 cout << ope << "\n";
60 }
61 void expand(int idx){
62 static int found = 0;
63 if(found){
64 while(!que[idx].empty()) que[idx].pop();
65 return;
66 }
67 int len = que[idx].size();
68 while(len--){
69 LL s = que[idx].front(), s2; que[idx].pop();
70 for(int i=1; i<5; ++i){
71 decode(s);
72 int r,c;
73 if(idx==0)
74 r = xx+dx[i], c = xy+dy[i];
75 else
76 r = xx-dx[i], c = xy-dy[i];
77 if(r<0 || c<0 || r==3 || c==3)
78 continue;
79 swap(eight[xx][xy], eight[r][c]);
80 s2 = encode();
81 if(mp[idx].find(s2)!=mp[idx].end())
82 continue;
83 mp[idx][s2] = make_pair(i,s);
84 if(mp[idx^1].find(s2)!=mp[idx^1].end()){
85 print(s2);
86 found=1;
87 return ;
88 }
89 else que[idx].push(s2);
90 }
91 }
92 }
93 void dbfs(){
94 mp[0].clear(), mp[1].clear();
95 LL tar=8;
96 for(int i=7; i>0; --i)
97 tar<<=4, tar |= i;
98 que[1].push(tar); mp[1][tar]=make_pair(-1,0);// 两者相等??
99 tar = encode();
100 que[0].push(tar); mp[0][tar] = make_pair(-1,0);
101 while(!que[0].empty() && !que[1].empty()){
102 if(que[0].size()<que[1].size())
103 expand(0);
104 else expand(1);
105 }
106 while(!que[0].empty())
107 expand(0);
108 while(!que[1].empty())
109 expand(1);
110 }
111 int main(){
112 std::ios::sync_with_stdio(false);
113 char c;
114 for(int i=0; i<3; ++i){
115 for(int j=0; j<3; ++j){
116 cin>>c;
117 if(c==‘x‘)
118 eight[i][j]=0, xx = i, xy = j;
119 else
120 eight[i][j]= c-‘0‘;
121 }
122 }
123 int cnt=0;
124 for(int i=0; i<9; ++i){
125 for(int pi=0; pi<i; ++pi)
126 if(eight[pi/3][pi%3] && eight[pi/3][pi%3]<eight[i/3][i%3])
127 cnt++;
128 }
129 if(cnt%2)
130 printf("unsolvable\n");
131 else
132 dbfs();
133 return 0;
134 }
bfs：
1 #include <iostream>
2 #include <map>
3 #include <algorithm>
4 #include <string>
5 #include <queue>
6 using namespace std;
7 typedef long long LL;
8
9 int eight[3][3], xx, xy, dx[]={0,0,-1,1,0}, dy[]={0,1,0,0,-1};
10 char dir[] = "orudl";
11 LL tar;
12
13 LL encode(){
14 LL s=eight[2][2];
15 for(int i=7; i>=0; --i){
16 s <<=4;
17 s |= eight[i/3][i%3];
18 }
19 return s;
20 }
21 void decode(LL s){
22 for(int i=0; i<9; ++i){
23 eight[i/3][i%3] = s%16;
24 if(s%16 == 0)
25 xx = i/3, xy = i%3;
26 s >>=4;
27 }
28 }
29 void print_state(LL s){
30 printf("s:%d,xx,xy:", s);
31 decode(s);
32 printf("%d,%d\n",xx,xy);
33 for(int i=0; i<3; ++i){
34 for(int j=0; j<3; ++j)
35 printf("%d ", eight[i][j]);
36 printf("\n");
37 }
38
39 }
40 queue<LL> que;
41 map<LL,pair<int,LL> > mp;// pair:d,ps
42
43 void print(LL s){
44 int d = mp[tar].first;
45 LL ts=s;
46 string ope;
47 while(d!=-1){
48 ope.push_back(dir[d]);
49 ts = mp[ts].second;
50 d = mp[ts].first;
51 }
52 reverse(ope.begin(), ope.end());
53 cout<< ope<< "\n";
54 }
55 void bfs(){
56 mp.clear();
57 LL s = encode(), s2;
58 que.push(s); mp[s] = make_pair(-1,0);
59 while(!que.empty()){
60 s = que.front(); que.pop();
61 for(int i=1; i<5; ++i){
62 decode(s);
63 int r,c;
64 r = xx+dx[i], c = xy+dy[i];
65 if(r<0 || c<0 || r==3 || c==3)
66 continue;
67 swap(eight[xx][xy], eight[r][c]);
68 s2 = encode();
69 if(mp.find(s2)!=mp.end())
70 continue;
71 mp[s2] = make_pair(i,s);
72 if(s2==tar){
73 print(s2);
74 return ;
75 }
76 else que.push(s2);
77 }
78 }
79 }
80 int main(){
81 std::ios::sync_with_stdio(false);
82 char c;
83 for(int i=0; i<3; ++i){
84 for(int j=0; j<3; ++j){
85 cin>>c;
86 if(c==‘x‘)
87 eight[i][j]=0, xx = i, xy = j;
88 else
89 eight[i][j]= c-‘0‘;
90 }
91 }
92 tar=8;
93 for(int i=7; i>0; --i)
94 tar<<=4, tar |= i;
95 int cnt=0;
96 for(int i=0; i<9; ++i){
97 for(int pi=0; pi<i; ++pi)
98 if(eight[pi/3][pi%3] && eight[pi/3][pi%3]<eight[i/3][i%3])
99 cnt++;
100 }
101 if(cnt%2)
102 printf("unsolvable\n");
103 else
104 bfs();
105 return 0;
106 }
时间： 2024-10-07 07:45:57