If grid[x][y] is 1, it can form a right triangle with an element of grid with value 1 in the same row and an element of grid with value 1 in the same column.
提示 2
So we just need to count the number of 1s in each row and column.
提示 3
For each x, y with grid[x][y] = 1 if there are row[x] 1s in the row x and col[y] 1s in column y, the answer should be added by (row[x] - 1) * (col[y] - 1).
