状态压缩+BFS。
1 /* 3088 */ 2 #include <iostream> 3 #include <cstdio> 4 #include <cstring> 5 #include <cstdlib> 6 #include <queue> 7 using namespace std; 8 9 #define MAXN 60000 10 #define MAXL 11 11 12 typedef struct { 13 char s[MAXL]; 14 int t; 15 } node_t; 16 17 node_t bn; 18 bool visit[MAXN]; 19 int end[3]; 20 int len; 21 22 int cal(char *s) { 23 int i, ret = 0; 24 25 for (i=0; i<len; ++i) 26 ret = 3*ret + s[i]; 27 return ret; 28 } 29 30 int bfs() { 31 int i, j, k, v; 32 int pre, cur; 33 queue<node_t> Q; 34 node_t nd; 35 36 v = cal(bn.s); 37 if (v == end[0] || v==end[1] || v==end[2]) 38 return 0; 39 memset(visit, false, sizeof(visit)); 40 visit[v] = true; 41 Q.push(bn); 42 43 while (!Q.empty()) { 44 nd = Q.front(); 45 Q.pop(); 46 for (i=1; i<len; ++i) { 47 if (nd.s[i] == nd.s[i-1]) 48 continue; 49 pre = nd.s[i-1]; 50 cur = nd.s[i]; 51 nd.s[i] = nd.s[i-1] = 3-(pre+cur); 52 v = cal(nd.s); 53 if (visit[v] == false) { 54 if (v==end[0] || v==end[1] || v==end[2]) 55 return nd.t + 1; 56 ++nd.t; 57 visit[v] = true; 58 Q.push(nd); 59 --nd.t; 60 } 61 nd.s[i-1] = pre; 62 nd.s[i] = cur; 63 } 64 } 65 66 return -1; 67 } 68 69 void init() { 70 int i, j, k; 71 72 end[0] = 0; 73 for (i=1; i<3; ++i) { 74 k = 0; 75 for (j=0; j<len; ++j) 76 k = 3*k + i; 77 end[i] = k; 78 } 79 } 80 81 int main() { 82 int t; 83 int i, j, k; 84 85 #ifndef ONLINE_JUDGE 86 freopen("data.in", "r", stdin); 87 freopen("data.out", "w", stdout); 88 #endif 89 90 scanf("%d", &t); 91 bn.t = 0; 92 while (t--) { 93 scanf("%s", bn.s); 94 len = strlen(bn.s); 95 init(); 96 for (i=0; i<len; ++i) { 97 if (bn.s[i] == 'r') bn.s[i] = 0; 98 if (bn.s[i] == 'g') bn.s[i] = 1; 99 if (bn.s[i] == 'b') bn.s[i] = 2; 100 } 101 k = bfs(); 102 if (k < 0) 103 puts("No solution!"); 104 else 105 printf("%d ", k); 106 } 107 108 return 0; 109 }