From 791e0b1ed4e87fc9299072f5cab1c47da43ec09d Mon Sep 17 00:00:00 2001
From: arpanjain97 <arpanjain97@gmail.com>
Date: Thu, 12 Oct 2017 17:12:54 +0530
Subject: [PATCH] Add Dijkstra's single source shortest path Algorithm in
 Greedy Algorithms directory

---
 Greedy Algorithms/Dijkstra.cpp | 103 +++++++++++++++++++++++++++++++++
 1 file changed, 103 insertions(+)
 create mode 100644 Greedy Algorithms/Dijkstra.cpp

diff --git a/Greedy Algorithms/Dijkstra.cpp b/Greedy Algorithms/Dijkstra.cpp
new file mode 100644
index 000000000..9cdcf077a
--- /dev/null
+++ b/Greedy Algorithms/Dijkstra.cpp	
@@ -0,0 +1,103 @@
+#include<iostream>
+#include<limits.h>
+
+using namespace std;
+
+//Wrapper class for storing a graph
+class Graph{
+	public:
+	int vertexNum;
+	int** edges;
+
+	//Constructs a graph with V vertices and E edges
+	Graph(int V){
+		this->vertexNum = V;
+		this->edges =(int**) malloc(V * sizeof(int*));
+		for(int i=0; i<V; i++)
+			this->edges[i] = (int*) calloc(V, sizeof(int));
+		
+	}
+
+	//Adds the given edge to the graph 
+	void addEdge(int src, int dst, int weight){
+		this->edges[src][dst] = weight;
+	}
+	
+
+};
+//Utility function to find minimum distance vertex in mdist
+int minDistance(int mdist[], bool vset[], int V){
+	int minVal = INT_MAX, minInd;
+	for(int i=0; i<V;i++)
+		if(vset[i] == false && mdist[i] < minVal){
+		minVal = mdist[i];
+		minInd = i;
+		}
+			
+	return minInd;
+}
+
+//Utility function to print distances
+void print(int dist[], int V){
+	cout<<"\nVertex  Distance"<<endl;
+	for(int i = 0; i < V; i++)
+		cout<<i<<"\t"<<dist[i]<<endl;
+}
+
+//The main function that finds the shortest path from given source
+//to all other vertices using Dijkstra's Algorithm.It doesn't work on negative
+//weights
+void Dijkstra(Graph graph, int src){
+	int V = graph.vertexNum;
+	int mdist[V]; //Stores updated distances to vertex
+	bool vset[V]; // vset[i] is true if the vertex i included
+			 // in the shortest path tree
+
+	//Initialise mdist and vset. Set distance of source as zero
+	for(int i=0; i<V; i++)
+		mdist[i] = INT_MAX, vset[i] = false;
+	
+	mdist[src] = 0;
+	
+	//iterate to find shortest path
+	for(int count = 0; count<V-1; count++){
+		int u = minDistance(mdist,vset,V);
+		
+		vset[u] = true;
+		
+		for(int v=0; v<V; v++){
+			if(!vset[v] && graph.edges[u][v] && mdist[u] + graph.edges[u][v] < mdist[v])
+				mdist[v] = mdist[u] + graph.edges[u][v];
+				
+		}
+	}
+
+	print(mdist, V);
+	
+	return;
+}
+
+//Driver Function
+int main(){
+	int V,E,gsrc;
+	int src,dst,weight;
+	cout<<"Enter number of vertices: ";
+	cin>>V;
+	cout<<"Enter number of edges: ";
+	cin>>E;
+	Graph G(V);
+	for(int i=0; i<E; i++){
+		cout<<"\nEdge "<<i+1<<"\nEnter source: ";
+		cin>>src;
+		cout<<"Enter destination: ";
+		cin>>dst;
+		cout<<"Enter weight: ";
+		cin>>weight;
+		G.addEdge(src, dst, weight);
+	}
+	cout<<"\nEnter source:";
+	cin>>gsrc;
+	Dijkstra(G,gsrc);
+
+	return 0;
+}