diff options
-rw-r--r-- | magic_squares_grid.c | 58 | ||||
-rw-r--r-- | magic_squares_grid.py | 38 |
2 files changed, 96 insertions, 0 deletions
diff --git a/magic_squares_grid.c b/magic_squares_grid.c new file mode 100644 index 0000000..c75dc94 --- /dev/null +++ b/magic_squares_grid.c @@ -0,0 +1,58 @@ +// 840. Magic Squares In Grid +#include "leetcode.h" + +/* + * a 3 * 3 magic square is a 3 x 3 grid filled with distinct numbers from 1 to 9 + * such that each row, column, and both diagonals all have the same sum. given a + * row x col 'grid' of integers, how many 3 x 3 contiguous magic square subgrids + * are there? note, while a magic square can only contain numbers from 1 to 9, + * 'grid' may contain numbers up to 15. + */ + +bool check(int **grid, int row, int col, int *map) { + for (int i = 0; i < 3; i++) + for (int j = 0; j < 3; j++) { + map[grid[row + i][col + j]]++; + if (map[grid[row + i][col + j]] > 1 || grid[row + i][col + j] > 9 || + grid[row + i][col + j] == 0) + return false; + } + int a = grid[row][col] + grid[row][col + 1] + grid[row][col + 2]; + int b = grid[row + 1][col] + grid[row + 1][col + 1] + grid[row + 1][col + 2]; + int c = grid[row + 2][col] + grid[row + 2][col + 1] + grid[row + 2][col + 2]; + if (a != 15 || b != 15 || c != 15) + return false; + int d = grid[row][col] + grid[row + 1][col] + grid[row + 2][col]; + int e = grid[row][col + 1] + grid[row + 1][col + 1] + grid[row + 2][col + 1]; + int f = grid[row][col + 2] + grid[row + 1][col + 2] + grid[row + 2][col + 2]; + if (d != 15 || e != 15 || f != 15) + return false; + int g = grid[row][col] + grid[row + 1][col + 1] + grid[row + 2][col + 2]; + int h = grid[row][col + 2] + grid[row + 1][col + 1] + grid[row + 2][col]; + if (g != 15 || h != 15) + return false; + return true; +} + +int numMagicSquaresInside(int **grid, int gridSize, int *gridColSize) { + if (gridSize < 3 || gridColSize[0] < 3) + return 0; + int *map = (int *)calloc(16, sizeof(int)), cnt = 0; + for (int i = 0; i + 2 < gridSize; i++) + for (int j = 0; j + 2 < gridColSize[0]; j++) { + if (check(grid, i, j, map)) + cnt++; + memset(map, 0, 16 * sizeof(int)); + } + free(map); + return cnt; +} + +int main() { + int g1[3][4] = {{4, 3, 8, 4}, {9, 5, 1, 9}, {2, 7, 6, 2}}, g2[1][1] = {{8}}, + gcs1 = 3, gcs2 = 1; + printf("%d\n", + numMagicSquaresInside((int **)g1, ARRAY_SIZE(g1), &gcs1)); // expect: 1 + printf("%d\n", + numMagicSquaresInside((int **)g2, ARRAY_SIZE(g2), &gcs2)); // expect: 0 +} diff --git a/magic_squares_grid.py b/magic_squares_grid.py new file mode 100644 index 0000000..213df01 --- /dev/null +++ b/magic_squares_grid.py @@ -0,0 +1,38 @@ +# 840. Magic Squares In Grid + +""" +a 3 3 magic square is a 3 x 3 grid filled with distinct numbers from 1 to 9 +such that each row, column, and both diagonals all have the same sum. given a +row x col 'grid' of integers, how many 3 x 3 contiguous magic square subgrids +are there? note, while a magic square can only contain numbers from 1 to 9, +'grid' may contain numbers up to 15. +""" + + +class Solution(object): + def numMagicSquaresInside(self, grid): + """ + :type grid: List[List[int]] + :rtype: int + """ + + def isMagic(i, j): + s = "".join( + str(grid[i + x / 3][j + x % 3]) for x in [0, 1, 2, 5, 8, 7, 6, 3] + ) + return grid[i][j] % 2 == 0 and ( + s in "43816729" * 2 or s in "43816729"[::-1] * 2 + ) + + return sum( + isMagic(i, j) + for i in range(len(grid) - 2) + for j in range(len(grid[0]) - 2) + if grid[i + 1][j + 1] == 5 + ) + + +if __name__ == "__main__": + obj = Solution() + print(obj.numMagicSquaresInside(grid=[[4, 3, 8, 4], [9, 5, 1, 9], [2, 7, 6, 2]])) + print(obj.numMagicSquaresInside(grid=[[8]])) |