Merge pull request #171 from AbhiY98/master

Added Topological Sorting

Author: ashwek

Graph/Topological-Sort.cpp

@@ -0,0 +1,46 @@
+#include <iostream>
+#include <vector>
+#include <algorithm>
+  using namespace std;
+
+int n , m; // For number of Vertices (V) and number of edges (E)
+vector< vector<int> > G;
+vector<bool> visited;
+vector<int> ans;
+
+void dfs(int v) {
+  visited[v] = true;
+  for (int u : G[v]) {
+    if (!visited[u])
+      dfs(u);
+  }
+  ans.push_back(v);
+}
+ 
+void topological_sort() {
+  visited.assign(n, false);
+  ans.clear();
+  for (int i = 0; i < n; ++i) {
+    if (!visited[i])
+      dfs(i);
+  }
+  reverse(ans.begin(), ans.end());
+}
+int main(){
+  cout << "Enter the number of vertices and the number of directed edges\n";
+  cin >> n >> m;
+  int x , y;
+  G.resize(n , vector<int>());
+  for(int i = 0 ; i < n ; ++i) {
+    cin >> x >> y;
+    x-- , y--; // to convert 1-indexed to 0-indexed
+    G[x].push_back(y);
+  }
+  topological_sort();
+  cout << "Topological Order : \n";
+  for(int v : ans) {
+    cout << v + 1 << ' '; // converting zero based indexing back to one based.
+  }
+  cout << '\n';
+  return 0;
+}