leetcode-problemset/leetcode-cn/originData/array-of-objects-to-matrix.json

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            "questionId": "2769",
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            "title": "Array of Objects to Matrix",
            "titleSlug": "array-of-objects-to-matrix",
            "content": "<p>Write a function that converts an array of objects&nbsp;<code>arr</code> into a matrix <code>m</code>.</p>\n\n<p><code>arr</code>&nbsp;is an array of objects or arrays. Each item in the array can be deeply nested with child arrays and child objects. It can also contain numbers, strings, booleans, and&nbsp;null values.</p>\n\n<p>The first row <code>m</code>&nbsp;should be the column names. If there is no nesting, the column names are the unique keys within the objects. If there is nesting, the column names&nbsp;are the respective paths in the object separated by <code>&quot;.&quot;</code>.</p>\n\n<p>Each of the remaining rows corresponds to an object in&nbsp;<code>arr</code>. Each value in the matrix corresponds to a value in an object. If a given object doesn&#39;t contain a value for a given column, the cell should contain an empty string&nbsp;<code>&quot;&quot;</code>.</p>\n\n<p>The colums in the matrix should be in <strong>lexographically ascending</strong> order.</p>\n\n<p>&nbsp;</p>\n<p><strong class=\"example\">Example 1:</strong></p>\n\n<pre>\n<strong>Input:</strong> \narr = [\n&nbsp; {&quot;b&quot;: 1, &quot;a&quot;: 2},\n&nbsp; {&quot;b&quot;: 3, &quot;a&quot;: 4}\n]\n<strong>Output:</strong> \n[\n&nbsp; [&quot;a&quot;, &quot;b&quot;],\n&nbsp; [2, 1],\n&nbsp; [4, 3]\n]\n\n<strong>Explanation:</strong>\nThere are two unique column names in the two objects: &quot;a&quot; and &quot;b&quot;.\n&quot;a&quot; corresponds with [2, 4].\n&quot;b&quot; coresponds with [1, 3].\n</pre>\n\n<p><strong class=\"example\">Example 2:</strong></p>\n\n<pre>\n<strong>Input:</strong> \narr = [\n&nbsp; {&quot;a&quot;: 1, &quot;b&quot;: 2},\n&nbsp; {&quot;c&quot;: 3, &quot;d&quot;: 4},\n&nbsp; {}\n]\n<strong>Output:</strong> \n[\n&nbsp; [&quot;a&quot;, &quot;b&quot;, &quot;c&quot;, &quot;d&quot;],\n&nbsp; [1, 2, &quot;&quot;, &quot;&quot;],\n&nbsp; [&quot;&quot;, &quot;&quot;, 3, 4],\n&nbsp; [&quot;&quot;, &quot;&quot;, &quot;&quot;, &quot;&quot;]\n]\n\n<strong>Explanation:</strong>\nThere are 4 unique column names: &quot;a&quot;, &quot;b&quot;, &quot;c&quot;, &quot;d&quot;.\nThe first object has values associated with &quot;a&quot; and &quot;b&quot;.\nThe second object has values associated with &quot;c&quot; and &quot;d&quot;.\nThe third object has no keys, so it is just a row of empty strings.\n</pre>\n\n<p><strong class=\"example\">Example 3:</strong></p>\n\n<pre>\n<strong>Input:</strong> \narr = [\n&nbsp; {&quot;a&quot;: {&quot;b&quot;: 1, &quot;c&quot;: 2}},\n&nbsp; {&quot;a&quot;: {&quot;b&quot;: 3, &quot;d&quot;: 4}}\n]\n<strong>Output:</strong> \n[\n&nbsp; [&quot;a.b&quot;, &quot;a.c&quot;, &quot;a.d&quot;],\n&nbsp; [1, 2, &quot;&quot;],\n&nbsp; [3, &quot;&quot;, 4]\n]\n\n<strong>Explanation:</strong>\nIn this example, the objects are nested. The keys represent the full path to each value separated by periods.\nThere are three paths: &quot;a.b&quot;, &quot;a.c&quot;, &quot;a.d&quot;.\n</pre>\n\n<p><strong class=\"example\">Example 4:</strong></p>\n\n<pre>\n<strong>Input:</strong> \narr = [\n&nbsp; [{&quot;a&quot;: null}],\n&nbsp; [{&quot;b&quot;: true}],\n&nbsp; [{&quot;c&quot;: &quot;x&quot;}]\n]\n<strong>Output:</strong> \n[\n&nbsp; [&quot;0.a&quot;, &quot;0.b&quot;, &quot;0.c&quot;],\n&nbsp; [null, &quot;&quot;, &quot;&quot;],\n&nbsp; [&quot;&quot;, true, &quot;&quot;],\n&nbsp; [&quot;&quot;, &quot;&quot;, &quot;x&quot;]\n]\n\n<strong>Explanation:</strong>\nArrays are also considered objects with their keys being their indices.\nEach array has one element so the keys are &quot;0.a&quot;, &quot;0.b&quot;, and &quot;0.c&quot;.\n</pre>\n\n<p><strong class=\"example\">Example 5:</strong></p>\n\n<pre>\n<strong>Input:</strong> \narr = [\n  {},\n&nbsp; {},\n&nbsp; {},\n]\n<strong>Output:</strong> \n[\n&nbsp; [],\n&nbsp; [],\n&nbsp; [],\n&nbsp; []\n]\n\n<strong>Explanation:</strong>\nThere are no keys so every row is an empty array.</pre>\n\n<p>&nbsp;</p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>1 &lt;= arr.length &lt;= 1000</code></li>\n\t<li><code>unique keys &lt;= 1000</code></li>\n</ul>\n",
            "translatedTitle": "将对象数组转换为矩阵",
            "translatedContent": "<p>编写一个函数，将对象数组&nbsp;<code>arr</code>&nbsp;转换为矩阵&nbsp;<code>m</code>&nbsp;。</p>\n\n<p><code>arr</code>&nbsp;是一个由对象组成的数组或一个数组。数组中的每个项都可以包含深层嵌套的子数组和子对象。它还可以包含数字、字符串、布尔值和空值。</p>\n\n<p>矩阵&nbsp;<code>m</code>&nbsp;的第一行应该是列名。如果没有嵌套，列名是对象中的唯一键。如果存在嵌套，列名是对象中相应路径，以点号&nbsp;<code>\".\"</code>&nbsp;分隔。</p>\n\n<p>剩余的每一行对应&nbsp;<code>arr</code>&nbsp;中的一个对象。矩阵中的每个值对应对象中的一个值。如果给定对象在给定列中没有值，则应该包含空字符串 <code>\"\"</code> 。</p>\n\n<p>矩阵中的列应按 <strong>字典升序</strong> 排列。</p>\n\n<p>&nbsp;</p>\n\n<p><strong class=\"example\">示例 1：</strong></p>\n\n<pre>\n<b>输入：</b>\narr = [\n&nbsp; {\"b\": 1, \"a\": 2},\n&nbsp; {\"b\": 3, \"a\": 4}\n]\n<b>输出：</b>\n[\n&nbsp; [\"a\", \"b\"],\n&nbsp; [2, 1],\n&nbsp; [4, 3]\n]\n\n<strong>解释：</strong>\n两个对象中有两个唯一的列名：\"a\"和\"b\"。 \n\"a\"对应[2, 4]。 \n\"b\"对应[1, 3]。\n</pre>\n\n<p><strong class=\"example\">示例 2：</strong></p>\n\n<pre>\n<b>输入：</b>\narr = [\n&nbsp; {\"a\": 1, \"b\": 2},\n&nbsp; {\"c\": 3, \"d\": 4},\n&nbsp; {}\n]\n<b>输出：</b>\n[\n&nbsp; [\"a\", \"b\", \"c\", \"d\"],\n&nbsp; [1, 2, \"\", \"\"],\n&nbsp; [\"\", \"\", 3, 4],\n&nbsp; [\"\", \"\", \"\", \"\"]\n]\n\n<strong>解释：</strong>\n有四个唯一的列名：\"a\"、\"b\"、\"c\"、\"d\"。 \n 第一个对象具有与\"a\"和\"b\"关联的值。 \n第二个对象具有与\"c\"和\"d\"关联的值。 \n第三个对象没有键，因此只是一行空字符串。\n</pre>\n\n<p><strong class=\"example\">示例 3：</strong></p>\n\n<pre>\n<b>输入：</b>\narr = [\n&nbsp; {\"a\": {\"b\": 1, \"c\": 2}},\n&nbsp; {\"a\": {\"b\": 3, \"d\": 4}}\n]\n<b>输出：</b>\n[\n&nbsp; [\"a.b\", \"a.c\", \"a.d\"],\n&nbsp; [1, 2, \"\"],\n&nbsp; [3, \"\", 4]\n]\n\n<b>解释：</b>\n在这个例子中，对象是嵌套的。键表示每个值的完整路径，路径之间用句点分隔。 \n有三个路径：\"a.b\"、\"a.c\"、\"a.d\"。\n</pre>\n\n<p><strong class=\"example\">示例 4：</strong></p>\n\n<pre>\n<b>输入：</b>\narr = [\n&nbsp; [{\"a\": null}],\n&nbsp; [{\"b\": true}],\n&nbsp; [{\"c\": \"x\"}]\n]\n<strong>输出：</strong> \n[\n&nbsp; [\"0.a\", \"0.b\", \"0.c\"],\n&nbsp; [null, \"\", \"\"],\n&nbsp; [\"\", true, \"\"],\n&nbsp; [\"\", \"\", \"x\"]\n]\n\n<strong>解释：</strong>\n数组也被视为具有索引为键的对象。 \n每个数组只有一个元素，所以键是\"0.a\"、\"0.b\"和\"0.c\"。\n</pre>\n\n<p><strong class=\"example\">示例 5：</strong></p>\n\n<pre>\n<b>输入：</b>\narr = [\n  {},\n&nbsp; {},\n&nbsp; {},\n]\n<b>输出：</b>\n[\n&nbsp; [],\n&nbsp; [],\n&nbsp; [],\n&nbsp; []\n]\n\n<strong>解释：</strong>\n没有键，所以每一行都是一个空数组。</pre>\n\n<p>&nbsp;</p>\n\n<p><strong>提示：</strong></p>\n\n<ul>\n\t<li><code>1 &lt;= arr.length &lt;= 1000</code></li>\n\t<li><code>unique keys &lt;= 1000</code></li>\n</ul>\n",
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                "How could you split the problem up into sub-problems?",
                "1.) Write a function that converts a single object into a dictionary that maps the path name to values. You can solve this recursively by keeping track of current path list.",
                "2.) Write a function that converts a list of dictionaries into a matrix. Start by creating a list of all possible paths in any of the dictionaries. This will represent the columns."
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