#376

#376 Implementation of Dijkstra's algorithm.

Author: ushmita4

Data Structures/Graphs/Dijkstra.c

@@ -0,0 +1,104 @@
+#include<stdio.h>
+#define size 50
+struct vertex{
+    int dist,par,processed;
+}V[size];
+int nv;
+//relax method is used to assign the shortest value to the node.
+void relax(int w[size][size],int u,int v){
+    //printf("RELAX %d  %d\n",u,v);
+    if(V[v].dist > V[u].dist + w[u][v]){
+        V[v].dist = V[u].dist + w[u][v];
+        V[v].par = u;
+    }
+}
+
+void initializeSingleSource(int src){
+    int i;
+    for(i = 0; i < nv; i++){
+        //printf("HERE ");
+       V[i].dist = 99999;
+       V[i].par = -1;
+       V[i].processed = 0;
+    }
+    V[src].dist = 0;
+}
+
+void dijkstra(int w[size][size],int src){
+    int i,j,k,ver,dmin;
+    initializeSingleSource(src);
+    for(i = 0; i < nv; i++){
+        dmin = 999999;
+        //printf("HERE ");
+        for(k = 0; k < nv; k++){
+            if(!V[k].processed && V[k].dist < dmin){
+                dmin = V[k].dist;
+                ver = k;
+            }
+           // printf("K LOOP %d %d %d %d \n",k,ver,V[k].processed,V[k].dist);
+        }
+        //printf("BETWEEN K AND J LOOP\n");
+        for(j = 0; j < nv; j++){
+            //printf("j = %d V[j].processed = %d w[ver][j] = %d ",j,V[j].processed,w[ver][j]);
+            if(!V[j].processed && w[ver][j]){
+                relax(w,ver,j);
+               // printf("J LOOP %d \n",ver);
+            }
+           // printf("J LOOP END\n");
+        }
+        V[ver].processed = 1;
+        //printf("I LOOP %d \n",V[ver].processed);
+    }
+}
+
+void printPath(int src,int dest){
+    if(dest == src){
+        printf("\n%d", src);
+        return;
+    }
+    printPath(src,V[dest].par);
+    printf(" ------> %d",dest);
+
+}
+int main(){
+    int i,j,src,dest;
+    int w[size][size];
+    printf("ENTER NO. OF VERTICES \n");
+    scanf("%d",&nv);
+//    int w[5][5] = {{0,10,0,5,0},
+//                {0,0,1,2,0},
+//                {0,0,0,0,4},
+//                {0,3,9,0,2},
+//                {7,0,6,0,0}};
+//    printf("-------- THE WEIGHT MATRIX --------\n");
+//    for(i = 0; i < nv; i++)
+//    {
+//        for(j = 0; j < nv; j++)
+//        {
+//            printf("w[%d][%d] = %d ",i,j,&w[i][j]);
+//        }
+//        printf("\n");
+//    }
+    printf("\nENTER THE WEIGHT MATRIX \n");
+    for(i = 0; i < nv; i++)
+    {
+        for(j = 0; j < nv; j++)
+        {
+            scanf("%d",&w[i][j]);
+        }
+    }
+    printf("\nENTER THE SOURCE \n");
+    scanf("%d",&src);
+    dijkstra(w,src);
+    do{
+        printf("\nENTER THE DESTINATION (ENTER -1 TO QUIT) \n");
+        scanf("%d",&dest);
+        if(dest != -1 && dest < nv){
+            printf("\nSHORTEST PATH WEIGHT = %d\n",V[dest].dist);
+            printf("\nPATH %d to %d IS",src,dest);
+            printPath(src,dest);
+        }
+    }while(dest != -1 && dest < nv);
+    return 0;
+}
+