Ultraviolet A Problem Solution: 10150-doublets

This problem can be solved by a BFS on a graph that modeling the doublet relationships. If the pair AAnd BForms a doublet, then there is a edge AAnd BIn the graph.

You can divide the dictionary into portions by word size, then handle each portion separately. To get a better RT, build each graph lazily only when needed.

Code:

1. /*************************************** **********************************
2. * Copyright (c) 2008 by liukaipeng *
3. * Liukaipeng at gmail dot com *
4. **************************************** *********************************/
6. /* @ Judge_id 00000 10150 C ++ "doublets "*/
8. # Include <cstring>
9. # Include <iostream>
10. # Include <fstream>
11. # Include <string>
12. # Include <map>
13. # Include <queue>
14. # Include <list>
15. # Include <vector>
16. # Include <map>
18. Using namespace STD;
20. Int const wordcount = 25200;
21. Int const wordsize = 20;
23. Typedef vector <char *> wordtable;
25. Struct strcomp
26. {Bool operator () (char * S1, char * S2) {return strcmp (S1, S2) <0 ;}};
27. Typedef Map <char *, Int, strcomp> wordmap;
29. Typedef vector <int> wordgraph;
31. Bool adjacent (char const * S1, char const * S2)
32. {
33. Bool adj = false;
34. For (INT I = 0; S1 [I]! = '/0'; ++ I ){
35. If (S1 [I]! = S2 [I]) {
36. Adj =! Adj;
37. If (! Adj) break;
38. }
39. }
40. Return adj;
41. }
43. Void build_wordgraph (wordtable const & wt, wordgraph & WG)
44. {
45. WG. Resize (wt. Size ());
46. For (INT I = 0; I <wt. Size ()-1; ++ I ){
47. For (Int J = I + 1; j <wt. Size (); ++ J ){
48. If (adjacent (wt [I], wt [J]) {
49. WG [I]. push_back (j );
50. WG [J]. push_back (I );
51. }
52. }
53. }
54. }
56. Bool get_doublets (wordgraph const & WG, int S, int T, list <int> & doublets)
57. {
58. Queue <int> q;
59. Vector <bool> visited (WG. Size (), false );
60. Vector <int> previous (WG. Size ());
61. Q. Push (s );
62. Visited [s] = true;
63. Bool found = false;
64. While (! Q. Empty ()){
65. Int v = Q. Front ();
66. Q. Pop ();
67. If (V = T ){
68. Found = true;
69. Break;
70. }
71. For (INT I = 0, size = WG [v]. Size (); I <size; ++ I ){
72. Int A = WG [v] [I];
73. If (! Visited [a]) {
74. Q. Push ();
75. Visited [a] = true;
76. Previous [a] = V;
77. }
78. }
79. }
81. If (found ){
82. For (; t! = S; t = previous [T]) doublets. push_front (t );
83. Doublets. push_front (t );
84. }
86. Return found;
87. }
89. Int main (INT argc, char * argv [])
90. {
91. # Ifndef online_judge
92. Filebuf In, out;
93. Cin. rdbuf (in. Open (string (argv [0]) + ". In"). c_str (), ios_base: In ));
94. Cout. rdbuf (out. Open (string (argv [0]) + ". Out"). c_str (), ios_base: Out ));
95. # Endif
97. Char words [wordcount] [wordsize];
98. Int nwords = 0;
99. For (; cin. Getline (words [nwords], wordsize) & words [nwords] [0]! = '/0 ';
100. ++ Nwords ){}
102. /* Index words by size */
103. Vector <wordtable> WTS (wordsize );
104. Vector <wordmap> WMS (wordsize );
105. For (INT I = 0; I <nwords; ++ I ){
106. Int size = strlen (words [I]);
107. WTS [size]. push_back (words [I]);
108. WMS [size]. insert (make_pair (words [I], WTS [size]. Size ()-1 ));
109. }
111. /* We will build wordgraph lazily */
112. Vector <wordgraph> WGS (wordsize );
114. Char source [wordsize], target [wordsize];
115. Int ncases = 0;
116. While (CIN> source> Target ){
117. If (ncases ++! = 0) cout <'/N ';
118. List <int> doublets;
119. Bool found = false;
120. Int size = strlen (source );
121. Wordtable & Wt = WTS [size];
122. Wordmap & WM = WMS [size];
123. Wordgraph & WG = WGS [size];
124. If (size = strlen (target )){
125. If (WG. Empty () build_wordgraph (wt, WG );
126. Found = get_doublets (WG, WM [Source], WM [target], doublets );
127. }
128. If (found ){
129. List <int>: iterator first = doublets. Begin (), last = doublets. End ();
130. For (; first! = Last; ++ first) cout <wt [* First] <'/N ';
131. } Else {
132. Cout <"no solution./N ";
133. }
134. }
136. Return 0;
137. }