1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
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
}
|