Added Topological Sort For Directed Acyclic Graph

Sorting/Topological Sort/topological_sort_using_DFS.cpp

@@ -0,0 +1,74 @@
+// Topological Sort For Directed Acyclic Graph
+// Using DFS
+// Ordering the task (nodes) such that there is no conflict
+#include <iostream>
+#include <bits/stdc++.h>
+using namespace std;
+void init() {
+#ifndef ONLINE_JUDGE
+    freopen("input.txt", "r", stdin);
+    freopen("output.txt", "w", stdout);
+#endif
+}
+template <typename T>
+class Graph {
+    int N;
+    map<T, list<T>> m;
+public:
+    Graph(int N) {
+        this->N = N;
+    }
+    void addEdge(T x, T y) {
+        m[x].push_back(y);
+    }
+    void dfs_helper(T node, map<T, bool> &visited, list<T> &ordering) {
+        // mark the node as visited
+        visited[node] = true;
+
+        for (auto neigh : m[node]) {
+            if (!visited[neigh]) {
+                dfs_helper(neigh, visited, ordering);
+            }
+        }
+        // If all the neigh are visited. Then put it in the list
+        ordering.push_front(node);
+        return;
+    }
+    void dfs() {
+        map<T, bool> visited;
+        list<T> ordering;
+
+        // Mark all nodes as unvisted in the beginning
+        for (auto node_pair : m) {
+            T node = node_pair.first;
+            visited[node] = false;
+        }
+
+        // make dfs call for every node as src that has dependency -> Means it has 1 or more neighbour
+        for (auto node_pair : m) {
+            T src = node_pair.first;
+            if (!visited[src]) {
+                dfs_helper(src, visited, ordering);
+            }
+        }
+
+        // ordering of the nodes such that there is no conflict
+        for (auto node : ordering) {
+            cout << node << " ,";
+        }
+    }
+};
+int main() {
+    init();
+    Graph<string> g(7);
+    g.addEdge("Python", "DataPreProcessing");
+    g.addEdge("Python", "PyTorch");
+    g.addEdge("Python", "ML");
+    g.addEdge("DataPreProcessing", "ML");
+    g.addEdge("PyTorch", "DL");
+    g.addEdge("ML", "DL");
+    g.addEdge("DL", "FaceRecognition");
+    g.addEdge("DataSet", "FaceRecognition");
+    g.dfs();
+    return 0;
+}