{ "data": { "question": { "questionId": "2193", "questionFrontendId": "2088", "categoryTitle": "Algorithms", "boundTopicId": 1121225, "title": "Count Fertile Pyramids in a Land", "titleSlug": "count-fertile-pyramids-in-a-land", "content": "
A farmer has a rectangular grid of land with m
rows and n
columns that can be divided into unit cells. Each cell is either fertile (represented by a 1
) or barren (represented by a 0
). All cells outside the grid are considered barren.
A pyramidal plot of land can be defined as a set of cells with the following criteria:
\n\n1
and all cells must be fertile.(r, c)
be the apex of the pyramid, and its height be h
. Then, the plot comprises of cells (i, j)
where r <= i <= r + h - 1
and c - (i - r) <= j <= c + (i - r)
.An inverse pyramidal plot of land can be defined as a set of cells with similar criteria:
\n\n1
and all cells must be fertile.(r, c)
be the apex of the pyramid, and its height be h
. Then, the plot comprises of cells (i, j)
where r - h + 1 <= i <= r
and c - (r - i) <= j <= c + (r - i)
.Some examples of valid and invalid pyramidal (and inverse pyramidal) plots are shown below. Black cells indicate fertile cells.
\n\nGiven a 0-indexed m x n
binary matrix grid
representing the farmland, return the total number of pyramidal and inverse pyramidal plots that can be found in grid
.
\n
Example 1:
\n\n\nInput: grid = [[0,1,1,0],[1,1,1,1]]\nOutput: 2\nExplanation: The 2 possible pyramidal plots are shown in blue and red respectively.\nThere are no inverse pyramidal plots in this grid. \nHence total number of pyramidal and inverse pyramidal plots is 2 + 0 = 2.\n\n\n
Example 2:
\n\n\nInput: grid = [[1,1,1],[1,1,1]]\nOutput: 2\nExplanation: The pyramidal plot is shown in blue, and the inverse pyramidal plot is shown in red. \nHence the total number of plots is 1 + 1 = 2.\n\n\n
Example 3:
\n\n\nInput: grid = [[1,1,1,1,0],[1,1,1,1,1],[1,1,1,1,1],[0,1,0,0,1]]\nOutput: 13\nExplanation: There are 7 pyramidal plots, 3 of which are shown in the 2nd and 3rd figures.\nThere are 6 inverse pyramidal plots, 2 of which are shown in the last figure.\nThe total number of plots is 7 + 6 = 13.\n\n\n
\n
Constraints:
\n\nm == grid.length
n == grid[i].length
1 <= m, n <= 1000
1 <= m * n <= 105
grid[i][j]
is either 0
or 1
.有一个 矩形网格 状的农场,划分为 m
行 n
列的单元格。每个格子要么是 肥沃的 (用 1
表示),要么是 贫瘠 的(用 0
表示)。网格图以外的所有与格子都视为贫瘠的。
农场中的 金字塔 区域定义如下:
\n\n1
且所有格子都是 肥沃的 。(r, c)
为金字塔的顶端且高度为 h
,那么金字塔区域内包含的任一格子 (i, j)
需满足 r <= i <= r + h - 1
且 c - (i - r) <= j <= c + (i - r)
。一个 倒金字塔 类似定义如下:
\n\n1
且所有格子都是 肥沃的 。(r, c)
为金字塔的顶端且高度为 h
,那么金字塔区域内包含的任一格子 (i, j)
需满足 r - h + 1 <= i <= r
且 c - (r - i) <= j <= c + (r - i)
。下图展示了部分符合定义和不符合定义的金字塔区域。黑色区域表示肥沃的格子。
\n\n\n\n给你一个下标从 0 开始且大小为 m x n
的二进制矩阵 grid
,它表示农场,请你返回 grid
中金字塔和倒金字塔的 总数目 。
\n\n
示例 1:
\n\n\n\n
输入:grid = [[0,1,1,0],[1,1,1,1]]\n输出:2\n解释:\n2 个可能的金字塔区域分别如上图蓝色和红色区域所示。\n这个网格图中没有倒金字塔区域。\n所以金字塔区域总数为 2 + 0 = 2 。\n\n\n
示例 2:
\n\n\n\n
输入:grid = [[1,1,1],[1,1,1]]\n输出:2\n解释:\n金字塔区域如上图蓝色区域所示,倒金字塔如上图红色区域所示。\n所以金字塔区域总数目为 1 + 1 = 2 。\n\n\n
示例 3:
\n\n\n\n输入:grid = [[1,0,1],[0,0,0],[1,0,1]]\n输出:0\n解释:\n网格图中没有任何金字塔或倒金字塔区域。\n\n\n
示例 4:
\n\n\n\n
输入:grid = [[1,1,1,1,0],[1,1,1,1,1],[1,1,1,1,1],[0,1,0,0,1]]\n输出:13\n解释:\n有 7 个金字塔区域。上图第二和第三张图中展示了它们中的 3 个。\n有 6 个倒金字塔区域。上图中最后一张图展示了它们中的 2 个。\n所以金字塔区域总数目为 7 + 6 = 13.\n\n\n
\n\n
提示:
\n\nm == grid.length
n == grid[i].length
1 <= m, n <= 1000
1 <= m * n <= 105
grid[i][j]
要么是 0
,要么是 1
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