Dijkstra's Algorithm added

General/Dijkstras Algorithm/amanag25_dijkstra'salgo.cpp

@@ -0,0 +1,109 @@
+#include<iostream>
+#include<set>
+#include<list>
+#include<algorithm>
+using namespace std;
+
+typedef struct nodes {
+   int dest;
+   int cost;
+}node;
+
+class Graph {
+   int n;
+   list<node> *adjList;
+   private:
+      void showList(int src, list<node> lt) {
+         list<node> :: iterator i;
+         node tempNode;
+
+         for(i = lt.begin(); i != lt.end(); i++) {
+            tempNode = *i;
+            cout << "(" << src << ")---("<<tempNode.dest << "|"<<tempNode.cost<<") ";
+         }
+         cout << endl;
+      }
+   public:
+      Graph() {
+         n = 0;
+      }
+
+      Graph(int nodeCount) {
+         n = nodeCount;
+         adjList = new list<node>[n];
+      }
+
+      void addEdge(int source, int dest, int cost) {
+         node newNode;
+         newNode.dest = dest;
+         newNode.cost = cost;
+         adjList[source].push_back(newNode);
+      }
+
+      void displayEdges() {
+         for(int i = 0; i<n; i++) {
+            list<node> tempList = adjList[i];
+            showList(i, tempList);
+         }
+      }
+
+      friend void dijkstra(Graph g, int *dist, int *prev, int start);
+};
+
+void dijkstra(Graph g, int *dist, int *prev, int start) {
+   int n = g.n;
+
+   for(int u = 0; u<n; u++) {
+      dist[u] = 9999;   //set as infinity
+      prev[u] = -1;    //undefined previous
+   }
+
+   dist[start] = 0;   //distance of start is 0
+   set<int> S;       //create empty set S
+   list<int> Q;
+
+   for(int u = 0; u<n; u++) {
+      Q.push_back(u);    //add each node into queue
+   }
+
+   while(!Q.empty()) {
+      list<int> :: iterator i;
+      i = min_element(Q.begin(), Q.end());
+      int u = *i; //the minimum element from queue
+      Q.remove(u);
+      S.insert(u); //add u in the set
+      list<node> :: iterator it;
+
+      for(it = g.adjList[u].begin(); it != g.adjList[u].end();it++) {
+         if((dist[u]+(it->cost)) < dist[it->dest]) { //relax (u,v)
+            dist[it->dest] = (dist[u]+(it->cost));
+            prev[it->dest] = u;
+         }
+      }
+   }
+}
+
+main() {
+   int n = 7;
+   Graph g(n);
+   int *dist = new int[n];
+   int *prev = new int[n];
+   int start = 0;
+   int edges;
+   cout<< "enter the number of edges";
+   cin>>edges;
+   for(int i=0;i<=edges*2;i++){
+       int source,dest,cost;
+       cout<<"enter edges in source-destination-cost format";
+       cin>>source>>dest>>cost;
+       g.addEdge(source,dest,cost);
+   }
+
+
+
+   dijkstra(g, dist, prev, start);
+
+   for(int i = 0; i<n; i++)
+      if(i != start)
+         cout<<start<<" to "<<i<<", Cost: "<<dist[i]<<" Previous: "<<prev[i]<<endl;
+}