Merge pull request #237 from jsourabh1/patch-1

Topological sort

Author: smv1999

Graph/Khan_algo.py

@@ -0,0 +1,77 @@
+'''
+author :saurabh jain
+to find whether a graph has a cycle or not not
+if not than print the topological sorting for them
+'''
+from collections import defaultdict
+
+
+class solution:
+
+    def __init__(self, vrt):
+        self.vrt = vrt
+        self.graph = defaultdict(list)
+
+    def edges(self, u, v):
+        global vertex,indegree
+        self.graph[u].append(v)
+        if u not in indegree.keys():
+            indegree[u]=0
+        if v not in indegree.keys():
+            indegree[v]=1
+
+        else:
+            indegree[v]+=1
+        vertex.add(u)
+        vertex.add(v)
+
+    def topological(self):
+        global vertex,indegree
+        q=[]
+        count=0
+        for i in vertex:
+            if indegree[i]==0:
+                q.append(i)
+
+        result=[]
+
+        while q:
+
+            current=q.pop(0)
+            count+=1
+            result.append(current)
+
+
+
+            for i in self.graph[current]:
+                indegree[i]-=1
+                if indegree[i]==0:
+                    q.append(i)
+
+        if count!=len(vertex):
+            print("there is no topolical string ")
+        else:
+            print(result)
+
+
+
+        return
+
+
+
+
+
+indegree=defaultdict()
+vertex=set()
+
+g =solution(6)
+g.edges(5, 2);
+g.edges(5, 0);
+g.edges(4, 0);
+g.edges(4, 1);
+g.edges(2, 3);
+g.edges(3, 1)
+print(indegree)
+print(vertex)
+
+g.topological()