adjacency list graph implementation in c (any libraries)

Question

I am working on a project where I make traceroutes to a certain IP address from 10-15 different IP addresses. Most of the traceroutes go along certain common routers on the way(hop) to the same destination. The resulting data gives me a graph. I think to represent this data the best way is an adjacency list. Is there any C library where I can get an instance of such a graph and add edges(hops) to it as I make different traceroute calls?

Answer 1

#include <stdio.h>
#include <stdlib.h>

// adjacency list implementation of graph using linked list in c

struct adj_node {
    int index;
    struct adj_node * next;
};

void makeadj(struct adj_node *nod,int adj) {
    struct adj_node *newadj=(struct adj_node *)malloc(sizeof(struct adj_node));
    newadj->index=adj;
    newadj->next=NULL;
    while(nod->next!=NULL)nod=nod->next;
    nod->next=newadj;
}

int main(){
    int i;
    struct adj_node graph[4],*temp;
    for(i=0;i<4;i++){
        graph[i].index=i;graph[i].next=NULL;
    }
    //example
    makeadj(&graph[0],2);
    makeadj(&graph[0],3);
    makeadj(&graph[1],2);
    makeadj(&graph[2],0);
    makeadj(&graph[2],1);
    makeadj(&graph[2],3);
    temp=&graph[2];
    while(temp->next!=NULL){
        printf("%d",temp->next->index);
        temp=temp->next;
    }
    return 0;
}

Answer 2

If you'll only ever need 10-15 IP addresses, you can get away with using a matrix. Otherwise, try a hash table which maps each vertex to a linked list. There are loads of free hash table implementations available.