add: 最大正方形

README.md

@@ -259,6 +259,11 @@ LeetCode 与 LintCode 解题记录。此为个人练习仓库，代码中对重
 
   - LeetCode 983. 最低票价 https://leetcode-cn.com/problems/minimum-cost-for-tickets/
 
+- [最大正方形](src/array/maximal-square.js)
+
+  - LeetCode 221. 最大正方形 https://leetcode-cn.com/problems/maximal-square/
+  - LintCode 436. 最大正方形 https://www.lintcode.com/problem/maximal-square/description
+
 ## 栈
 
 - [最大矩阵](src/stack/maximal-rectangle.js)

src/array/maximal-square.js

@@ -0,0 +1,25 @@
+/**
+ * @param {character[][]} matrix
+ * @return {number}
+ */
+export const maximalSquare = function (matrix) {
+  if (!matrix || !matrix[0]) return 0
+
+  const rows = matrix.length
+  const cols = matrix[0].length
+  let max = 0
+
+  const dp = new Array(rows).fill().map(_ => new Array(cols).fill(0))
+
+  for (let n = 0; n < rows; n++) {
+    for (let i = 0; i < cols; i++) {
+      if (Number(matrix[n][i]) === 1) {
+        if (n === 0 || i === 0) dp[n][i] = 1
+        else dp[n][i] = Math.min(dp[n - 1][i], dp[n][i - 1], dp[n - 1][i - 1]) + 1 // 找规律
+        max = Math.max(max, dp[n][i])
+      }
+    }
+  }
+
+  return max * max
+}

test/array/maximal-square.test.js

@@ -0,0 +1,15 @@
+import { maximalSquare } from '../../src/array/maximal-square'
+
+test('最大正方形', () => {
+  expect(maximalSquare([
+    [1, 0, 1, 0, 0],
+    [1, 0, 1, 1, 1],
+    [1, 1, 1, 1, 1],
+    [1, 0, 0, 1, 0]
+  ])).toBe(4)
+
+  expect(maximalSquare([
+    [0, 0, 0],
+    [1, 1, 1]
+  ])).toBe(1)
+})