feat: 2088 Count Fertile Pyramids in a Land : DP

Author: upupming

Diff for: README.md

@@ -14,6 +14,7 @@
 - Google KickStart [kick-start](kick-start)
 - LeetCode [leetcode](leetcode)
     - [残酷刷题](leetcode/残酷刷题)
+        - 想加入残酷刷题群的朋友可以联系我，[残酷刷题群2020年会总结](https://zhuanlan.zhihu.com/p/341323903)、[群规链接](http://board.cruelcoding.com/rules.html)
 - 伪代码 [pseudoCode](pseudoCode)
 - 其他的都是之前刷 PAT 时候的题目
 

Diff for: leetcode/残酷刷题/2088. Count Fertile Pyramids in a Land.ts

@@ -0,0 +1,34 @@
+function countPyramids (grid: number[][]): number {
+  const [m, n] = [grid.length, grid[0].length]
+  let ans = 0
+  const dpUp: number[][] = []
+  const dpDown: number[][] = []
+
+  const [left, right]: [number[][], number[][]] = [[], []]
+  for (let i = 0; i < m; i++) {
+    left[i] = []; right[i] = []
+    for (let j = 0; j < n; j++) {
+      if (grid[i][j] === 1) left[i][j] = (left[i][j - 1] ?? 0) + 1
+      else left[i][j] = 0
+    }
+    for (let j = n - 1; j >= 0; j--) {
+      if (grid[i][j] === 1) right[i][j] = (right[i][j + 1] ?? 0) + 1
+      else right[i][j] = 0
+    }
+  }
+  for (let i = 0; i < m; i++) {
+    dpUp[i] = []
+    for (let j = 0; j < n; j++) {
+      dpUp[i][j] = Math.min((dpUp[i - 1]?.[j] ?? 0) + 1, left[i][j], right[i][j])
+      if (dpUp[i][j] > 1) ans += dpUp[i][j] - 1
+    }
+  }
+  for (let i = m - 1; i >= 0; i--) {
+    dpDown[i] = []
+    for (let j = 0; j < n; j++) {
+      dpDown[i][j] = Math.min((dpDown[i + 1]?.[j] ?? 0) + 1, left[i][j], right[i][j])
+      if (dpDown[i][j] > 1) ans += dpDown[i][j] - 1
+    }
+  }
+  return ans
+};

Diff for: leetcode/残酷刷题/README.md

@@ -69,6 +69,7 @@
 - 1478. Allocate Mailboxes
     - DP + 货仓选址
 - 1277. Count Square Submatrices with All Ones
+- 2088. Count Fertile Pyramids in a Land
 
 #### 状态压缩