The Settlers of Catan

#include<bits/stdc++.h>

using namespace std;

vector<int>graph[30];

bool color[30][30];

int node,edge;

int dfs(int u)
{
    int i,len = graph[u].size(),mx=0;

    for(i=0;i<len;i++)
    {
        if(!color[u][graph[u][i]])
        {
            color[u][graph[u][i]] = true;

            color[graph[u][i]][u] = true;

            mx = max(mx,1+dfs(graph[u][i]));

            color[u][graph[u][i]] = false;

            color[graph[u][i]][u] = false;
        }
    }

    return mx;
}

int main()
{
    int ans,i,u,v,mx;

    while(scanf("%d%d",&node,&edge) &&node &&edge)
    {
        for(i=1;i<=edge;i++)
        {
            scanf("%d%d",&u,&v);

            graph[u].push_back(v);

            graph[v].push_back(u);
        }

        ans = 0;

        for(i=0;i<node;i++)
        {
            memset(color,false,sizeof(color));

            mx = dfs(i);

            ans = max(ans,mx);
        }

        printf("%d\n",ans);

        for(i=0;i<=node;i++)
        {
            graph[i].clear();
        }
    }

    return 0;
}