代码如下：
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 queue<LL> que; 30 map<LL,pair<int,LL> > mp;// pair:d,ps 31 32 void print(LL s){ 33 int d = mp[tar].first; 34 LL ts=s; 35 string ope; 36 while(d!=-1){ 37 ope.push_back(dir[d]); 38 ts = mp[ts].second; 39 d = mp[ts].first; 40 } 41 reverse(ope.begin(), ope.end()); 42 cout<< ope<< " "; 43 } 44 void bfs(){ 45 mp.clear(); 46 LL s = encode(), s2; 47 que.push(s); mp[s] = make_pair(-1,0); 48 while(!que.empty()){ 49 s = que.front(); que.pop(); 50 for(int i=1; i<5; ++i){ 51 decode(s); 52 int r,c; 53 r = xx+dx[i], c = xy+dy[i]; 54 if(r<0 || c<0 || r==3 || c==3) 55 continue; 56 swap(eight[xx][xy], eight[r][c]); 57 s2 = encode(); 58 if(mp.find(s2)!=mp.end()) 59 continue; 60 mp[s2] = make_pair(i,s); 61 if(s2==tar){ 62 print(s2); 63 return ; 64 } 65 else que.push(s2); 66 } 67 } 68 } 69 int main(){ 70 std::ios::sync_with_stdio(false); 71 char c; 72 for(int i=0; i<3; ++i){ 73 for(int j=0; j<3; ++j){ 74 cin>>c; 75 if(c=='x') 76 eight[i][j]=0, xx = i, xy = j; 77 else 78 eight[i][j]= c-'0'; 79 } 80 } 81 tar=8; 82 for(int i=7; i>0; --i) 83 tar<<=4, tar |= i; 84 int cnt=0; 85 for(int i=0; i<9; ++i){ 86 for(int pi=0; pi<i; ++pi) 87 if(eight[pi/3][pi%3] && eight[pi/3][pi%3]<eight[i/3][i%3]) 88 cnt++; 89 } 90 if(cnt%2) 91 printf("unsolvable "); 92 else 93 bfs(); 94 return 0; 95 }
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 queue<LL> que[2]; 29 map<LL,pair<int,LL> > mp[2];// pair:d,ps 30 31 void print(LL s){ 32 int d = mp[0][s].first; 33 LL ts=s; 34 string ope; 35 while(d!=-1){ 36 ope.push_back(dir[d]); 37 ts = mp[0][ts].second; 38 d = mp[0][ts].first; 39 } 40 reverse(ope.begin(), ope.end()); 41 cout<< ope; 42 ope.clear(), d = mp[1][s].first, ts = s; 43 while(d!=-1){ 44 ope.push_back(dir[d]); 45 ts = mp[1][ts].second; 46 d = mp[1][ts].first; 47 } 48 cout << ope << " "; 49 } 50 void expand(int idx){ 51 static int found = 0; 52 if(found){ 53 while(!que[idx].empty()) que[idx].pop(); 54 return; 55 } 56 int len = que[idx].size(); 57 while(len--){ 58 LL s = que[idx].front(), s2; que[idx].pop(); 59 for(int i=1; i<5; ++i){ 60 decode(s); 61 int r,c; 62 if(idx==0) 63 r = xx+dx[i], c = xy+dy[i]; 64 else 65 r = xx-dx[i], c = xy-dy[i]; 66 if(r<0 || c<0 || r==3 || c==3) 67 continue; 68 swap(eight[xx][xy], eight[r][c]); 69 s2 = encode(); 70 if(mp[idx].find(s2)!=mp[idx].end()) 71 continue; 72 mp[idx][s2] = make_pair(i,s); 73 if(mp[idx^1].find(s2)!=mp[idx^1].end()){ 74 print(s2); 75 found=1; 76 return ; 77 } 78 else que[idx].push(s2); 79 } 80 } 81 } 82 void dbfs(){ 83 mp[0].clear(), mp[1].clear(); 84 LL tar=8; 85 for(int i=7; i>0; --i) 86 tar<<=4, tar |= i; 87 que[1].push(tar); mp[1][tar]=make_pair(-1,0);// 两者相等?? 88 tar = encode(); 89 que[0].push(tar); mp[0][tar] = make_pair(-1,0); 90 while(!que[0].empty() && !que[1].empty()){ 91 if(que[0].size()<que[1].size()) 92 expand(0); 93 else expand(1); 94 } 95 while(!que[0].empty()) 96 expand(0); 97 while(!que[1].empty()) 98 expand(1); 99 } 100 int main(){ 101 freopen("C:\Users\yyf\Documents\CppFiles\in.txt", "r", stdin); 102 std::ios::sync_with_stdio(false); 103 char c; 104 for(int i=0; i<3; ++i){ 105 for(int j=0; j<3; ++j){ 106 cin>>c; 107 if(c=='x') 108 eight[i][j]=0, xx = i, xy = j; 109 else 110 eight[i][j]= c-'0'; 111 } 112 } 113 int cnt=0; 114 for(int i=0; i<9; ++i){ 115 for(int pi=0; pi<i; ++pi) 116 if(eight[pi/3][pi%3] && eight[pi/3][pi%3]<eight[i/3][i%3]) 117 cnt++; 118 } 119 if(cnt%2) 120 printf("unsolvable "); 121 else 122 dbfs(); 123 return 0; 124 }
A*:
1 #include <iostream> 2 #include <map> 3 #include <algorithm> 4 #include <string> 5 #include <queue> 6 #include <set> 7 using namespace std; 8 typedef long long LL; 9 10 int eight[3][3], xx, xy, dx[]={0,-1,1,0}, dy[]={1,0,0,-1}; 11 char dir[] = "rudl"; 12 LL init, tar; 13 14 LL encode(){ 15 LL s=eight[2][2]; 16 for(int i=7; i>=0; --i){ 17 s <<=4; 18 s |= eight[i/3][i%3]; 19 } 20 return s; 21 } 22 void decode(LL s){ 23 for(int i=0; i<9; ++i){ 24 eight[i/3][i%3] = s%16; 25 if(s%16 == 0) 26 xx = i/3, xy = i%3; 27 s >>=4; 28 } 29 } 30 class Node { 31 public: 32 LL s, ps; 33 int f,g,h,d; 34 Node (LL _s=0, LL _ps=0, int _d=-1, int _f=0, int _g=0, int _h=0){ 35 s = _s, ps = _ps, f = _f, g = _g, h = _h, d = _d; 36 } 37 int operator<(const Node & b) const { 38 return this->f < b.f || (this->f==b.f && this->s<b.s); 39 } 40 }; 41 42 multiset<Node> closed, open; 43 map<LL, multiset<Node>::iterator> inOpen, inClosed; 44 45 void print(Node nd){ 46 int d = nd.d; 47 LL ts = nd.s; 48 string ope; 49 while(d!=-1){ 50 ope.push_back(dir[d]); 51 auto itc = inClosed[nd.ps]; 52 nd = *itc; 53 d = nd.d; 54 } 55 reverse(ope.begin(), ope.end()); 56 cout<< ope<< " "; 57 } 58 int hn(LL s){ 59 decode(s); 60 int cnt=0; 61 for(int i=0; i<9; ++i){ 62 if(eight[i/3][i%3] != (i+1)%9) cnt++; 63 } 64 return cnt; 65 } 66 void astar(){ 67 init = encode(); 68 int inith = hn(init); 69 Node start = Node(init, 0, -1, inith, 0, inith); 70 open.insert(start); 71 while(!open.empty()){ 72 Node tn = *open.begin(); inOpen.erase(tn.s); open.erase(tn); 73 LL ts = tn.s, s2; 74 int tf = tn.f, tg = tn.g, th = tn.h; 75 for(int i=0; i<4; ++i){ 76 decode(ts); 77 int r = xx+dx[i], c=xy+dy[i]; 78 if(r<0 || c<0 || r==3 || c==3) continue; 79 swap(eight[r][c], eight[xx][xy]); 80 s2 = encode(); 81 int g = tg+1, h = hn(s2), f = g+h; 82 Node nd = Node(s2, ts, i, f, g, h); 83 if(s2 == tar){ 84 inClosed[tn.s]= closed.insert(tn); 85 inClosed[nd.s]= closed.insert(nd); 86 print(nd); 87 return; 88 } 89 auto ito = inOpen.find(s2), itc = inClosed.find(s2); 90 if(ito == inOpen.end() && itc == inClosed.end()){ 91 inOpen[nd.s]=open.insert(nd); 92 } 93 else if(ito == inOpen.end() && f < itc->second->f){ 94 closed.erase(itc->second); inClosed.erase(itc); 95 inOpen[nd.s]=open.insert(nd); 96 } 97 else if(itc == inClosed.end() && f < ito->second->f){ 98 // que 里有相同s不同f的node 99 open.erase(ito->second), inOpen[nd.s]=open.insert(nd); 100 } 101 } 102 inClosed[tn.s] = closed.insert(tn); 103 } 104 } 105 int main(){ 106 std::ios::sync_with_stdio(false); 107 char c; 108 for(int i=0; i<3; ++i){ 109 for(int j=0; j<3; ++j){ 110 cin>>c; 111 if(c=='x') 112 eight[i][j]=0, xx = i, xy = j; 113 else 114 eight[i][j]= c-'0'; 115 } 116 } 117 tar=8; 118 for(int i=7; i>0; --i) 119 tar<<=4, tar |= i; 120 int cnt=0; 121 for(int i=0; i<9; ++i){ 122 for(int pi=0; pi<i; ++pi) 123 if(eight[pi/3][pi%3] && eight[pi/3][pi%3]<eight[i/3][i%3]) 124 cnt++; 125 } 126 if(cnt%2) 127 printf("unsolvable "); 128 else 129 astar(); 130 return 0; 131 }