UVA 539 The Settlers of Catan

 

CODE：

 

#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <cstring>
using namespace std;

#define MAXN  30
#define INF 0X3F3F3F3F
int G[MAXN][MAXN];
bool vis[MAXN][MAXN];
int ans, n, m;

void init()
{
    memset(G, 0, sizeof(G));
    ans = -INF;
}


void dfs(int u, int cur)
{
    if(cur > ans) ans = cur;
    for(int v = 0; v < n; v++)
    {
        if(G[u][v] && !vis[u][v] && !vis[v][u])
        {
            vis[u][v] = vis[v][u] = 1;
            dfs(v, cur+1);
            vis[u][v] = vis[v][u] = 0;
        }
    }
}

int main()
{
    while(scanf("%d%d", &n, &m) && ( n || m))
    {
        init();
        while(m--)
        {
            int u, v;
            scanf("%d%d", &u, &v);
            G[u][v] = G[v][u] = 1;
        }
        for(int v = 0; v < n; v++)
        {
            memset(vis, 0, sizeof(vis));
            dfs(v, 0);
        }
        printf("%d\n", ans);
    }
    return 0;
}