Merge pull request #4399 from marimeireles/master

Merged by aniket965

C++/topological_search_using_dfs/Makefile

@@ -0,0 +1,7 @@
+tp1: main.cpp Makefile
+	$(CXX) -O2 -std=c++11 main.cpp -o tp1
+
+clean:
+	rm tp1
+
+all: tp1

C++/topological_search_using_dfs/main.cpp

@@ -0,0 +1,103 @@
+#include <iostream>
+#include <vector>
+#include <string>
+#include <set>
+#include <algorithm>
+#include <unordered_map>
+
+using namespace std;
+
+int DFS(unordered_map<int, vector<int>>& graph, int key, unordered_map<int, int>& marked, int *time, unordered_map<int, int>& finalTime) {
+    *time = *time + 1;
+    marked[key] = 1;
+    for (int neighbor : graph[key]) {
+        if (marked[neighbor] == 0) {
+            if (DFS(graph, neighbor, marked, time, finalTime)) return 1;
+        }
+        else if (marked[neighbor] == 1) {
+            marked[neighbor] = 2;
+            return 1;
+        }
+    }
+    marked[key] = 2;
+    *time = *time + 1;
+    finalTime[key] = *time;
+    return 0;
+}
+
+int main(int argc, char const *argv[]) {
+
+    FILE* inputFile = fopen(argv[1], "r");
+
+    int numberVertices, numberEdges;
+    fscanf(inputFile, "%d %d\n", &numberVertices, &numberEdges);
+
+    //creates and fills a graph using inputFile data
+    unordered_map<int, vector<int>> graph;
+    //creates a vector that will hold the keys of DFS walking order
+    set<int> order;
+    //creates a vector that will check if the graph is of type 1 or 2
+    set<int> defineType;
+
+    int vertexA, vertexB;
+    for (int i = 0; i < numberEdges; ++i) {
+        fscanf(inputFile, "%d %d\n", &vertexA, &vertexB);
+        //insert vertices on a set to make sure they'll be unique
+        order.insert(vertexA);
+        order.insert(vertexB);
+        //insert vertices on graph
+        graph[vertexA].push_back(vertexB);
+        defineType.insert(vertexA);
+    }
+    fclose(inputFile);
+
+    //marks vertices as unvisiteds
+    unordered_map<int, int> marked;
+    for (auto vertex : graph) {
+        marked[vertex.first] = 0;
+    }
+
+    //creates a final time hashtable for graph
+    unordered_map<int, int> finalTime;
+
+    //inserts content of set on a vector so it can be ordered
+    vector<int> vertices;
+    for (int v : order) {
+        vertices.push_back(v);
+    }
+    sort(vertices.begin(), vertices.end());
+
+    FILE* outputFile = fopen(argv[2], "w");
+
+    //runs DFS
+    int isCycle = 0;
+    int time = 0;
+    for (int vertex : vertices) {
+        if (marked[vertex] != 2) {
+            if (DFS(graph, vertex, marked, &time, finalTime) == 1) {
+                fprintf(outputFile, "0 -1\n");
+                return 0;
+            }
+        }
+    }
+
+    //define the type of graph
+    if (defineType.size() < numberVertices - 1)
+        fprintf(outputFile, "2 ");
+    else fprintf(outputFile, "1 ");
+
+    //sort vertices according to finalTime in growing order
+    sort(vertices.begin(), vertices.end(), [&finalTime](int a, int b) {
+        return finalTime[a] < finalTime[b];
+    });
+
+    //prints output
+    for (int v : vertices) {
+        if (v == vertices.back()) fprintf(outputFile, "%d\n", v);
+        else fprintf(outputFile, "%d, ", v);
+    }
+
+    fclose(outputFile);
+
+    return 0;
+}