Merge pull request #73 from Modernbeast02/main

Course Schedule in C++

LeetCode/Course Schedule/C++/Solution.cpp

@@ -0,0 +1,38 @@
+class Solution {
+public:
+    vector<int> findOrder(int numCourses, vector<vector<int>>& prerequisites) {
+        // just print the topo sort if all indegree at the end are zero
+
+        vector<int>indegree(numCourses, 0);
+        vector<int>adj[numCourses];
+        vector<int>ans;
+        for(auto it : prerequisites){
+            adj[it[1]].push_back(it[0]); // created graph
+            indegree[it[0]]++; // created indegree array
+        }
+        queue<int>q;
+        for(int i = 0; i < numCourses; i++){
+            if(indegree[i] == 0){
+                q.push(i);
+            }
+        }
+        while(!q.empty()){
+            int top = q.front();
+            ans.push_back(top);
+            q.pop();
+            for(auto it : adj[top]){
+                indegree[it]--;
+                if(indegree[it] == 0){
+                    q.push(it);
+                }
+            }
+        }
+        for(int i = 0; i < numCourses; i++){
+            if(indegree[i] != 0){
+                vector<int> dummy;
+                return dummy;
+            }
+        }
+        return ans;
+    }
+};

LeetCode/Course Schedule/Problem.md

@@ -0,0 +1,42 @@
+<h2><a href="https://leetcode.com/problems/course-schedule-ii/">210. Course Schedule II</a></h2><h3>Medium</h3><hr><div><p>There are a total of <code>numCourses</code> courses you have to take, labeled from <code>0</code> to <code>numCourses - 1</code>. You are given an array <code>prerequisites</code> where <code>prerequisites[i] = [a<sub>i</sub>, b<sub>i</sub>]</code> indicates that you <strong>must</strong> take course <code>b<sub>i</sub></code> first if you want to take course <code>a<sub>i</sub></code>.</p>
+
+<ul>
+	<li>For example, the pair <code>[0, 1]</code>, indicates that to take course <code>0</code> you have to first take course <code>1</code>.</li>
+</ul>
+
+<p>Return <em>the ordering of courses you should take to finish all courses</em>. If there are many valid answers, return <strong>any</strong> of them. If it is impossible to finish all courses, return <strong>an empty array</strong>.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre><strong>Input:</strong> numCourses = 2, prerequisites = [[1,0]]
+<strong>Output:</strong> [0,1]
+<strong>Explanation:</strong> There are a total of 2 courses to take. To take course 1 you should have finished course 0. So the correct course order is [0,1].
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre><strong>Input:</strong> numCourses = 4, prerequisites = [[1,0],[2,0],[3,1],[3,2]]
+<strong>Output:</strong> [0,2,1,3]
+<strong>Explanation:</strong> There are a total of 4 courses to take. To take course 3 you should have finished both courses 1 and 2. Both courses 1 and 2 should be taken after you finished course 0.
+So one correct course order is [0,1,2,3]. Another correct ordering is [0,2,1,3].
+</pre>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<pre><strong>Input:</strong> numCourses = 1, prerequisites = []
+<strong>Output:</strong> [0]
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= numCourses &lt;= 2000</code></li>
+	<li><code>0 &lt;= prerequisites.length &lt;= numCourses * (numCourses - 1)</code></li>
+	<li><code>prerequisites[i].length == 2</code></li>
+	<li><code>0 &lt;= a<sub>i</sub>, b<sub>i</sub> &lt; numCourses</code></li>
+	<li><code>a<sub>i</sub> != b<sub>i</sub></code></li>
+	<li>All the pairs <code>[a<sub>i</sub>, b<sub>i</sub>]</code> are <strong>distinct</strong>.</li>
+</ul>
+</div>