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// 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<vector<int>> &board) {
string begin = "", end = "123450";
vector<vector<int>> 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<string> vis;
vis.insert(begin);
queue<pair<string, int>> 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
}
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