leetcode

0 class Solution {

1 using type_t = pair<uint32_t, uint32_t>;

2

3 static type_t encode(const vector<vector<int>> &board) {

4 uint32_t n2p = 0; // number to position

5 uint32_t p2n = 0; // position to number

6

7 for (int i = 0; i < 2; i++) {

8 for (int j = 0; j < 3; j++) {

9 const int idx = i * 3 + j;

10 n2p |= idx << (board[i][j] * 3);

11 p2n |= board[i][j] << (idx * 3);

12 }

13 }

14

15 return {n2p, p2n};

16 }

17

18 public:

19 int slidingPuzzle(const vector<vector<int>> &board) const {

20 static const vector<vector<int>> adj = {{1, 3}, {0, 2, 4}, {1, 5}, {0, 4}, {1, 3, 5}, {2, 4}};

21

22 unordered_set<uint32_t> seen;

23 queue<type_t> q;

24

25 q.push(encode(board));

26 for (int lvl = 0; !q.empty(); lvl++) {

27 for (int k = size(q); k > 0; k--) {

28 const auto [n2p, p2n] = q.front();

29 q.pop();

30

31 if (n2p == 0x23445) return lvl;

32

33 const auto p = n2p & 0x7; // position of zero

34 for (const auto sp : adj[p]) { // position to swap

35 const auto sn = (p2n >> (sp * 3)) & 0x7; // number to swap

36

37 const auto sn2p = (n2p & ~((0x7 << (sn * 3)) | (0x7 << (0 * 0)))) | (p << (sn * 3)) | sp;

38 const auto sp2n = (p2n & ~((0x7 << (sp * 3)) | (0x7 << (p * 3)))) | (sn << (p * 3));

39

40 if (!seen.count(sn2p)) {

41 q.emplace(sn2p, sp2n);

42 seen.insert(sn2p);

43 }

44 }

45 }

46 }

47

48 return -1;

49 }

50 };