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Diffstat (limited to 'other/shortest_path_binary_matrix.cpp')
-rw-r--r-- | other/shortest_path_binary_matrix.cpp | 55 |
1 files changed, 55 insertions, 0 deletions
diff --git a/other/shortest_path_binary_matrix.cpp b/other/shortest_path_binary_matrix.cpp new file mode 100644 index 0000000..fd586fe --- /dev/null +++ b/other/shortest_path_binary_matrix.cpp @@ -0,0 +1,55 @@ +// 1091. Shortest Path in Binary Matrix +#include "leetcode.h" + +/* + * given an n x n binary matrix 'grid', return the length of the shortest clear + * path in the matrix. if there is no clear path, return -1. a clear path in a + * binary matrix is a path from the top-left cell (ie. 0,0) to the bottom-right + * cell (ie. n - 1, n - 1) such thatyt + * - all the visited cells are of the path 0 + * - all the adjacent cells of the path are 8-directionally connected (ie. they + * are different and they share an edge of a corner) the length of a clear path + * is the number of visited cells of this path + */ + +class Solution { +public: + int shortestPathBinaryMatrix(vector<vector<int>> &grid) { + if (grid[0][0] || grid.back().back()) + return -1; + int ans = 2, n = 1, nr = grid[0].size() - 1, nc = grid.size() - 1; + queue<pair<int, int>> qp; + if (!nr && !nc) + return 1 - (grid[0][0] << 1); + qp.push({0, 0}); + grid[0][0] = -1; + while (n) { + while (n--) { + auto [cx, cy] = qp.front(); + qp.pop(); + for (int i = max(0, cx - 1), lmtx = min(cx + 1, nr); i <= lmtx; i++) + for (int j = max(0, cy - 1), lmty = min(cy + 1, nc); j <= lmty; j++) { + if (i == nr && j == nc) + return ans; + if (!grid[j][i]) { + grid[j][i] = -1; + qp.push({i, j}); + } + } + } + ans++; + n = qp.size(); + } + return -1; + } +}; + +int main() { + Solution obj; + vvd g1 = {{0, 1}, {1, 0}}; + vvd g2 = {{0, 0, 0}, {1, 1, 0}, {1, 1, 0}}; + vvd g3 = {{1, 0, 0}, {1, 1, 0}, {1, 1, 0}}; + printf("%d\n", obj.shortestPathBinaryMatrix(g1)); // expect: 2 + printf("%d\n", obj.shortestPathBinaryMatrix(g2)); // expect: 4 + printf("%d\n", obj.shortestPathBinaryMatrix(g3)); // expect: -1 +} |