// 773. Sliding Puzzle #include "leetcode.h" /* * on an empty 2 x 3 board there are five tiles labeled from 1 to 5 and an empty * square represented by 0. a move consists of choosing 0 and a 4-directionall * adjacent number and swapping it. the state of the board is solved if and only * if the board is '[[1,2,3],[4,5,0]]'. given the puzzle 'board', return the * least number of moves required so that the state of the board is solved. if * it is impossible for the state of the board to be solved, return -1 */ class Solution { public: int slidingPuzzle(vector> &board) { string begin = "", end = "123450"; vector> moves = {{1, 3}, {0, 2, 4}, {1, 5}, {0, 4}, {1, 3, 5}, {2, 4}}; for (int i = 0; i < board.size(); i++) for (int j = 0; j < board[0].size(); j++) begin += to_string(board[i][j]); unordered_set vis; vis.insert(begin); queue> qp; qp.push({begin, 0}); while (!qp.empty()) { auto p = qp.front(); qp.pop(); string curr = p.first; int dist = p.second, idx = curr.find("0"); if (curr == end) return dist; for (auto &i : moves[idx]) { string next = curr; swap(next[idx], next[i]); if (!vis.count(next)) { vis.insert(next); qp.push({next, dist + 1}); } } } return -1; } }; int main() { Solution obj; vvd(int) b1 = {{1, 2, 3}, {4, 0, 5}}, b2 = {{1, 2, 3}, {5, 4, 0}}, b3 = {{4, 1, 2}, {5, 0, 3}}; printf("%d\n", obj.slidingPuzzle(b1)); // expect 1 printf("%d\n", obj.slidingPuzzle(b2)); // expect -1 printf("%d\n", obj.slidingPuzzle(b3)); // expect 5 }