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Dijkstra_Bruteforce.c
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Dijkstra_Bruteforce.c
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#include <stdio.h>
#include <string.h>
#include <limits.h>
#include <stdlib.h>
#define int long long int
struct adjacencylist
{
int nodeindex;
int weight;
struct adjacencylist* adj;
};
struct adjacencylist *graph[100002],*traverse;
int nodes,edges,distance,a,b,update,parent,pick,cur,ok=0,adjacent,edge,c1,c2,small,stop,source,heapsize;
int index,answer_exist,prev,cnt;
struct adjacencylist *ptr;
int swap(int *a,int *b){ int temp=*a; *a=*b; *b=temp;}
int minimum(int a, int b){ if(a<=b)return a; else return b;}
int add_edge(int a,int b,int distance)
{
traverse=(struct adjacencylist*)malloc(sizeof(struct adjacencylist));
traverse->adj=graph[a];
traverse->nodeindex=b;
traverse->weight=distance;
graph[a]=traverse;
}
int dijkstra_minheap(int *adjac,int* dist,int *previous,int* visit)
{
int till=nodes;
while(till>0)
{
int mini=1e18,pick,ok=0;
for(int i=1;i<=nodes;i++)
{
if(mini>dist[i] && visit[i]==0)
{
mini=dist[i];
pick=i;
ok=1;
}
}
if(ok==0)break;
//Relax the nodes adjacent to picked vertexk
visit[pick]=1;
ptr=graph[pick];
ok=0,adjacent,edge;
stop=adjac[pick];
while(stop>0 && dist[pick]!=LLONG_MAX)
{
adjacent=ptr->nodeindex;
edge=ptr->weight;
if(visit[adjacent]==0 && dist[pick]+edge<dist[adjacent] && dist[pick]!=LLONG_MAX && edge>=0)
{
dist[adjacent]=dist[pick]+edge;//relaxation of nodes adjacent to picked vertex
previous[adjacent]=pick;
}
ptr=ptr->adj;
stop--;
}
till--;
}
}
int print_path(int *previous)
{
int shortestpath[nodes+1];
index=1,answer_exist=1,prev=nodes;
shortestpath[index]=nodes;
index++;
while(1)
{
prev=previous[prev];
if(prev==-1){answer_exist=0;break;}
shortestpath[index]=prev;
if(prev==1){break;}
index++;
}
if(answer_exist==0){printf("-1\n");return 0;}
for(int i=index;i>0;i--) printf("%lld ",shortestpath[i]);
printf("\n");
}
int main()
{
scanf("%lld%lld",&nodes,&edges); //nodes and edges
int adjac[nodes+1],previous[nodes+1],map[nodes+1];;
memset(adjac,0,sizeof(adjac));
//graph input in linked list begins
for(int i=0;i<edges;i++)
{
scanf("%lld%lld%lld",&a,&b,&distance);
adjac[a]++;
add_edge(a,b,distance);
add_edge(b,a,distance);
adjac[b]++;
}
//Djkstra algorithm
source=1;
int visit[nodes+1],dist[nodes+1];
for(int i=1;i<=nodes;i++){dist[i]=LLONG_MAX; visit[i]=0;previous[i]=-1;}
dist[source]=0;
//dijkstra
dijkstra_minheap(&adjac,&dist,&previous,&visit);
//printing path from source to node to destination node 'n'
print_path(&previous);
return 0;
}