algorithms/221-maximal-square.ipynb

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    "### [最大正方形](https://leetcode-cn.com/problems/maximal-square/)\n",
    "\n",
    "在一个由`'0'`和`'1'`组成的二维矩阵内，找到只包含`'1'`的最大正方形，并返回其面积。\n",
    "\n",
    "#### 示例 1：\n",
    "```\n",
    "输入：matrix = [\n",
    "        [\"1\",\"0\",\"1\",\"0\",\"0\"],\n",
    "        [\"1\",\"0\",\"1\",\"1\",\"1\"],\n",
    "        [\"1\",\"1\",\"1\",\"1\",\"1\"],\n",
    "        [\"1\",\"0\",\"0\",\"1\",\"0\"]\n",
    "    ]\n",
    "输出：4\n",
    "```\n",
    "\n",
    "#### 示例 2：\n",
    "```\n",
    "输入：matrix = [\n",
    "        [\"0\",\"1\"],\n",
    "        [\"1\",\"0\"]\n",
    "    ]\n",
    "输出：1\n",
    "```\n",
    "\n",
    "#### 示例 3：\n",
    "```\n",
    "输入：matrix = [[\"0\"]]\n",
    "输出：0\n",
    "```\n",
    "\n",
    "#### 提示：\n",
    "\n",
    "- `m == matrix.length`\n",
    "- `n == matrix[i].length`\n",
    "- `1 <= m, n <= 300`\n",
    "- `matrix[i][j] 为 '0' 或 '1'`"
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    "from typing import List\n",
    "\n",
    "def maximalSquare(matrix: List[List[str]]) -> int:\n",
    "    if not (matrix and matrix[0]):\n",
    "        return 0\n",
    "    m, n = len(matrix), len(matrix[0])\n",
    "    \n",
    "    def countMaxSide(r, c):\n",
    "        maxSide = 1\n",
    "        maxK = min(m - r, n - c)\n",
    "        for k in range(1, maxK):\n",
    "            flag = True\n",
    "            if matrix[r + k][c + k] == '0':\n",
    "                break\n",
    "            for i in range(k):\n",
    "                if matrix[r + k][c + i] == '0' or matrix[r + i][c + k] == '0':\n",
    "                    flag = False\n",
    "                    break\n",
    "            \n",
    "            if flag:\n",
    "                maxSide = max(maxSide, k + 1)\n",
    "            else:\n",
    "                break\n",
    "        return maxSide\n",
    "                \n",
    "    ans = 0\n",
    "    for r in range(m):\n",
    "        for c in range(n):\n",
    "            if matrix[r][c] == '1':\n",
    "                side = countMaxSide(r, c)\n",
    "                ans = max(ans, side * side)\n",
    "    return ans"
   ]
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   "source": [
    "maximalSquare([[\"0\", \"1\"], [\"1\", \"0\"]])"
   ]
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   "source": [
    "matrix = [\n",
    "    [\"1\",\"0\",\"1\",\"0\",\"0\"],\n",
    "    [\"1\",\"0\",\"1\",\"1\",\"1\"],\n",
    "    [\"1\",\"1\",\"1\",\"1\",\"1\"],\n",
    "    [\"1\",\"0\",\"0\",\"1\",\"0\"]\n",
    "]\n",
    "maximalSquare(matrix)"
   ]
  },
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     "execution_count": 15,
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   ],
   "source": [
    "maximalSquare([[\"1\",\"1\"],[\"1\",\"1\"]])"
   ]
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