1// RUN: %clang_cc1 -std=c++11 -fsyntax-only %s
2
3typedef unsigned long uint64_t;
4
5struct Board {
6  uint64_t State;
7  bool Failed;
8
9  constexpr Board() : State(0), Failed(false) {}
10  constexpr Board(const Board &O) : State(O.State), Failed(O.Failed) {}
11  constexpr Board(uint64_t State, bool Failed = false) :
12    State(State), Failed(Failed) {}
13  constexpr Board addQueen(int Row, int Col) {
14    return Board(State | ((uint64_t)Row << (Col * 4)));
15  }
16  constexpr int getQueenRow(int Col) {
17    return (State >> (Col * 4)) & 0xf;
18  }
19  constexpr bool ok(int Row, int Col) {
20    return okRecurse(Row, Col, 0);
21  }
22  constexpr bool okRecurse(int Row, int Col, int CheckCol) {
23    return Col == CheckCol ? true :
24           getQueenRow(CheckCol) == Row ? false :
25           getQueenRow(CheckCol) == Row + (Col - CheckCol) ? false :
26           getQueenRow(CheckCol) == Row + (CheckCol - Col) ? false :
27           okRecurse(Row, Col, CheckCol + 1);
28  }
29  constexpr bool at(int Row, int Col) {
30    return getQueenRow(Col) == Row;
31  }
32  constexpr bool check(const char *, int=0, int=0);
33};
34
35constexpr Board buildBoardRecurse(int N, int Col, const Board &B);
36constexpr Board buildBoardScan(int N, int Col, int Row, const Board &B);
37constexpr Board tryBoard(const Board &Try,
38                         int N, int Col, int Row, const Board &B) {
39  return Try.Failed ? buildBoardScan(N, Col, Row, B) : Try;
40}
41constexpr Board buildBoardScan(int N, int Col, int Row, const Board &B) {
42  return Row == N ? Board(0, true) :
43         B.ok(Row, Col) ?
44         tryBoard(buildBoardRecurse(N, Col + 1, B.addQueen(Row, Col)),
45                  N, Col, Row+1, B) :
46         buildBoardScan(N, Col, Row + 1, B);
47}
48constexpr Board buildBoardRecurse(int N, int Col, const Board &B) {
49  return Col == N ? B : buildBoardScan(N, Col, 0, B);
50}
51constexpr Board buildBoard(int N) {
52  return buildBoardRecurse(N, 0, Board());
53}
54
55constexpr Board q8 = buildBoard(8);
56
57constexpr bool Board::check(const char *p, int Row, int Col) {
58  return
59    *p == '\n' ? check(p+1, Row+1, 0) :
60    *p == 'o' ? at(Row, Col) && check(p+1, Row, Col+1) :
61    *p == '-' ? !at(Row, Col) && check(p+1, Row, Col+1) :
62    *p == 0 ? true :
63    false;
64}
65static_assert(q8.check(
66    "o-------\n"
67    "------o-\n"
68    "----o---\n"
69    "-------o\n"
70    "-o------\n"
71    "---o----\n"
72    "-----o--\n"
73    "--o-----\n"), "");
74