From 0efd7cb312bb39abdcbbb525e8991faf17c7b4ec Mon Sep 17 00:00:00 2001
From: Sugata Roy <sugata98@gmail.com>
Date: Fri, 5 Oct 2018 00:18:53 +0530
Subject: [PATCH] Creat Dijktra-algo.c

C program implementing Dijkstra's Algorithm
---
 Algorithms-C/Dijktras-Algo/Dijktra-algo.c | 91 +++++++++++++++++++++++
 1 file changed, 91 insertions(+)
 create mode 100644 Algorithms-C/Dijktras-Algo/Dijktra-algo.c

diff --git a/Algorithms-C/Dijktras-Algo/Dijktra-algo.c b/Algorithms-C/Dijktras-Algo/Dijktra-algo.c
new file mode 100644
index 0000000..68b0796
--- /dev/null
+++ b/Algorithms-C/Dijktras-Algo/Dijktra-algo.c
@@ -0,0 +1,91 @@
+#include<stdio.h>
+#include<conio.h>
+#define INFINITY 9999
+#define MAX 10
+ 
+void dijkstra(int G[MAX][MAX],int n,int startnode);
+ 
+int main()
+{
+    int G[MAX][MAX],i,j,n,u;
+    printf("Enter no. of vertices:");
+    scanf("%d",&n);
+    printf("\nEnter the adjacency matrix:\n");
+    
+    for(i=0;i<n;i++)
+        for(j=0;j<n;j++)
+            scanf("%d",&G[i][j]);
+    
+    printf("\nEnter the starting node:");
+    scanf("%d",&u);
+    dijkstra(G,n,u);
+    
+    return 0;
+}
+ 
+void dijkstra(int G[MAX][MAX],int n,int startnode)
+{
+ 
+    int cost[MAX][MAX],distance[MAX],pred[MAX];
+    int visited[MAX],count,mindistance,nextnode,i,j;
+    
+    //pred[] stores the predecessor of each node
+    //count gives the number of nodes seen so far
+    //create the cost matrix
+    for(i=0;i<n;i++)
+        for(j=0;j<n;j++)
+            if(G[i][j]==0)
+                cost[i][j]=INFINITY;
+            else
+                cost[i][j]=G[i][j];
+    
+    //initialize pred[],distance[] and visited[]
+    for(i=0;i<n;i++)
+    {
+        distance[i]=cost[startnode][i];
+        pred[i]=startnode;
+        visited[i]=0;
+    }
+    
+    distance[startnode]=0;
+    visited[startnode]=1;
+    count=1;
+    
+    while(count<n-1)
+    {
+        mindistance=INFINITY;
+        
+        //nextnode gives the node at minimum distance
+        for(i=0;i<n;i++)
+            if(distance[i]<mindistance&&!visited[i])
+            {
+                mindistance=distance[i];
+                nextnode=i;
+            }
+            
+            //check if a better path exists through nextnode            
+            visited[nextnode]=1;
+            for(i=0;i<n;i++)
+                if(!visited[i])
+                    if(mindistance+cost[nextnode][i]<distance[i])
+                    {
+                        distance[i]=mindistance+cost[nextnode][i];
+                        pred[i]=nextnode;
+                    }
+        count++;
+    }
+ 
+    //print the path and distance of each node
+    for(i=0;i<n;i++)
+        if(i!=startnode)
+        {
+            printf("\nDistance of node%d=%d",i,distance[i]);
+            printf("\nPath=%d",i);
+            
+            j=i;
+            do
+            {
+                j=pred[j];
+                printf("<-%d",j);
+            }while(j!=startnode);
+    }