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            "questionId": "1309",
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            "title": "Sort Items by Groups Respecting Dependencies",
            "titleSlug": "sort-items-by-groups-respecting-dependencies",
            "content": "<p>There are&nbsp;<code>n</code>&nbsp;items each&nbsp;belonging to zero or one of&nbsp;<code>m</code>&nbsp;groups where <code>group[i]</code>&nbsp;is the group that the <code>i</code>-th item belongs to and it&#39;s equal to <code>-1</code>&nbsp;if the <code>i</code>-th item belongs to no group. The items and the groups are zero indexed. A group can have no item belonging to it.</p>\n\n<p>Return a sorted list of the items such that:</p>\n\n<ul>\n\t<li>The items that belong to the same group are next to each other in the sorted list.</li>\n\t<li>There are some&nbsp;relations&nbsp;between these items where&nbsp;<code>beforeItems[i]</code>&nbsp;is a list containing all the items that should come before the&nbsp;<code>i</code>-th item in the sorted array (to the left of the&nbsp;<code>i</code>-th item).</li>\n</ul>\n\n<p>Return any solution if there is more than one solution and return an <strong>empty list</strong>&nbsp;if there is no solution.</p>\n\n<p>&nbsp;</p>\n<p><strong>Example 1:</strong></p>\n\n<p><strong><img alt=\"\" src=\"https://assets.leetcode.com/uploads/2019/09/11/1359_ex1.png\" style=\"width: 191px; height: 181px;\" /></strong></p>\n\n<pre>\n<strong>Input:</strong> n = 8, m = 2, group = [-1,-1,1,0,0,1,0,-1], beforeItems = [[],[6],[5],[6],[3,6],[],[],[]]\n<strong>Output:</strong> [6,3,4,1,5,2,0,7]\n</pre>\n\n<p><strong>Example 2:</strong></p>\n\n<pre>\n<strong>Input:</strong> n = 8, m = 2, group = [-1,-1,1,0,0,1,0,-1], beforeItems = [[],[6],[5],[6],[3],[],[4],[]]\n<strong>Output:</strong> []\n<strong>Explanation:</strong>&nbsp;This is the same as example 1 except that 4 needs to be before 6 in the sorted list.\n</pre>\n\n<p>&nbsp;</p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>1 &lt;= m &lt;= n &lt;= 3 * 10<sup>4</sup></code></li>\n\t<li><code>group.length == beforeItems.length == n</code></li>\n\t<li><code>-1 &lt;= group[i] &lt;= m - 1</code></li>\n\t<li><code>0 &lt;= beforeItems[i].length &lt;= n - 1</code></li>\n\t<li><code>0 &lt;= beforeItems[i][j] &lt;= n - 1</code></li>\n\t<li><code>i != beforeItems[i][j]</code></li>\n\t<li><code>beforeItems[i]&nbsp;</code>does not contain&nbsp;duplicates elements.</li>\n</ul>\n",
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            "exampleTestcases": "8\n2\n[-1,-1,1,0,0,1,0,-1]\n[[],[6],[5],[6],[3,6],[],[],[]]\n8\n2\n[-1,-1,1,0,0,1,0,-1]\n[[],[6],[5],[6],[3],[],[4],[]]",
            "categoryTitle": "Algorithms",
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                {
                    "name": "Depth-First Search",
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                    "name": "Breadth-First Search",
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                    "name": "Graph",
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                    "name": "Topological Sort",
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                    "lang": "C++",
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                    "code": "class Solution {\npublic:\n    vector<int> sortItems(int n, int m, vector<int>& group, vector<vector<int>>& beforeItems) {\n        \n    }\n};",
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                    "code": "class Solution {\n    public int[] sortItems(int n, int m, int[] group, List<List<Integer>> beforeItems) {\n        \n    }\n}",
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                    "lang": "Python",
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                    "code": "class Solution(object):\n    def sortItems(self, n, m, group, beforeItems):\n        \"\"\"\n        :type n: int\n        :type m: int\n        :type group: List[int]\n        :type beforeItems: List[List[int]]\n        :rtype: List[int]\n        \"\"\"\n        ",
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                    "code": "class Solution:\n    def sortItems(self, n: int, m: int, group: List[int], beforeItems: List[List[int]]) -> List[int]:\n        ",
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                    "lang": "C",
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                    "code": "\n\n/**\n * Note: The returned array must be malloced, assume caller calls free().\n */\nint* sortItems(int n, int m, int* group, int groupSize, int** beforeItems, int beforeItemsSize, int* beforeItemsColSize, int* returnSize){\n\n}",
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                    "lang": "C#",
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                    "code": "public class Solution {\n    public int[] SortItems(int n, int m, int[] group, IList<IList<int>> beforeItems) {\n        \n    }\n}",
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                    "code": "/**\n * @param {number} n\n * @param {number} m\n * @param {number[]} group\n * @param {number[][]} beforeItems\n * @return {number[]}\n */\nvar sortItems = function(n, m, group, beforeItems) {\n    \n};",
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                    "code": "# @param {Integer} n\n# @param {Integer} m\n# @param {Integer[]} group\n# @param {Integer[][]} before_items\n# @return {Integer[]}\ndef sort_items(n, m, group, before_items)\n    \nend",
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                    "code": "class Solution {\n    func sortItems(_ n: Int, _ m: Int, _ group: [Int], _ beforeItems: [[Int]]) -> [Int] {\n        \n    }\n}",
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                    "code": "func sortItems(n int, m int, group []int, beforeItems [][]int) []int {\n    \n}",
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                    "code": "object Solution {\n    def sortItems(n: Int, m: Int, group: Array[Int], beforeItems: List[List[Int]]): Array[Int] = {\n        \n    }\n}",
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                    "code": "class Solution {\n    fun sortItems(n: Int, m: Int, group: IntArray, beforeItems: List<List<Int>>): IntArray {\n        \n    }\n}",
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                    "lang": "Rust",
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                    "code": "impl Solution {\n    pub fn sort_items(n: i32, m: i32, group: Vec<i32>, before_items: Vec<Vec<i32>>) -> Vec<i32> {\n        \n    }\n}",
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                    "lang": "PHP",
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                    "code": "class Solution {\n\n    /**\n     * @param Integer $n\n     * @param Integer $m\n     * @param Integer[] $group\n     * @param Integer[][] $beforeItems\n     * @return Integer[]\n     */\n    function sortItems($n, $m, $group, $beforeItems) {\n        \n    }\n}",
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                    "lang": "TypeScript",
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                    "code": "function sortItems(n: number, m: number, group: number[], beforeItems: number[][]): number[] {\n\n};",
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                    "code": "(define/contract (sort-items n m group beforeItems)\n  (-> exact-integer? exact-integer? (listof exact-integer?) (listof (listof exact-integer?)) (listof exact-integer?))\n\n  )",
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                    "lang": "Erlang",
                    "langSlug": "erlang",
                    "code": "-spec sort_items(N :: integer(), M :: integer(), Group :: [integer()], BeforeItems :: [[integer()]]) -> [integer()].\nsort_items(N, M, Group, BeforeItems) ->\n  .",
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                    "code": "defmodule Solution do\n  @spec sort_items(n :: integer, m :: integer, group :: [integer], before_items :: [[integer]]) :: [integer]\n  def sort_items(n, m, group, before_items) do\n\n  end\nend",
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            "hints": [
                "Think of it as a graph problem.",
                "We need to find a topological order on the dependency graph.",
                "Build two graphs, one for the groups and another for the items."
            ],
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