diff options
Diffstat (limited to 'magic_squares_grid.c')
-rw-r--r-- | magic_squares_grid.c | 58 |
1 files changed, 58 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 +} |