leetcode-courseschedule

LC207COURSESCHEDULE

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+import java.util.ArrayList;
+import java.util.List;
+
+public class LC207CourseSchedule {
+    public static void main(String[] args) {
+
+        LC207CourseSchedule obj=new LC207CourseSchedule();
+        int numCourses=2;
+        int[][] prerequisites=new int[][]{{1,0}};
+        System.out.println(obj.canFinish(numCourses,prerequisites));
+    }//sample main function
+
+        public boolean canFinish(int numCourses, int[][] prerequisites) {
+            int[] v=new int[numCourses];
+            int[] path=new int[numCourses];
+            List<List<Integer>> list=new ArrayList<>();
+
+            for (int i = 0; i < numCourses; i++) {
+                list.add(new ArrayList<>());
+            }
+            for(int i=0;i<prerequisites.length;i++){
+                int a=prerequisites[i][1];
+                int b=prerequisites[i][0];
+                list.get(a).add(b);
+            }
+            for(int i=0;i<numCourses;i++){
+                if(v[i]==0){
+                    if(dfs(i,list,v,path)==true){
+                        return false;
+                    }
+                }
+            }
+            return true;
+        }
+
+        public boolean dfs(int node,List<List<Integer>> list,int[] v,int[] path){
+            v[node]=1;
+            path[node]=1;
+            List<Integer> l=list.get(node);
+            for(int i=0;i<l.size();i++){
+                int a=l.get(i);
+                if(v[a]==0){
+                    if(dfs(a,list,v,path)==true){
+                        return true;
+                    }
+                }
+
+                else if(path[a]==1){
+                    return true;
+                }
+            }
+            path[node]=0;
+            return false;
+
+
+        }
+    }
+