Create 29 - Course Schedule.cpp

Author: sudhir5595

29 - Course Schedule.cpp

@@ -0,0 +1,61 @@
+class Solution {
+public:
+    
+    bool cycle_find(vector < vector <int> > &graph, int numCourses){
+        
+        // Create a vector to store indegrees of all 
+    // vertices. Initialize all indegrees as 0.
+        
+        vector <int> in_degree(numCourses,0);
+        
+        for(int i = 0; i<numCourses; i++){
+            for(int j = 0; j<graph[i].size(); j++){
+                in_degree[graph[i][j]]++;
+            }
+        }
+        
+        // Create an queue and enqueue all vertices with indegree 0
+        queue <int> q;
+        for(int i = 0; i<numCourses; i++){
+            if(in_degree[i] == 0){
+                q.push(i);
+            }
+        }
+        
+        // Initialize count of visited vertices 
+        int cnt = 0; 
+        
+        // Create a vector to store result (A topological ordering of the vertices) 
+        vector<int> top_order; 
+        
+        while(!q.empty()){
+            int temp = q.front();
+            top_order.push_back(temp);
+            q.pop();
+            
+            for(int i = 0; i<graph[temp].size(); i++){
+                in_degree[graph[temp][i]]--;
+                if(in_degree[graph[temp][i]] == 0){
+                    q.push(graph[temp][i]);
+                }
+            }
+            cnt++;
+        }
+        
+        if(cnt != numCourses){
+            return 0;
+        }
+        return 1;
+    }
+    
+    bool canFinish(int numCourses, vector<vector<int>>& prerequisites) {
+        
+        vector < vector <int> > graph(numCourses);
+        int n = prerequisites.size();
+        
+        for(int i = 0; i<n; i++){
+            graph[prerequisites[i][0]].push_back(prerequisites[i][1]);
+        }
+        return cycle_find(graph,numCourses);
+    }
+};