poj1081

dfs

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

#define maxn 65

bool g[maxn][maxn];
int ans;
int n;
int c[maxn];
bool vis[maxn];
int lonely[maxn];

void check(int t)
{
    memset(vis, 0, sizeof(vis));
    memset(lonely, 0, sizeof(lonely));
    for (int i = 0; i < t; i++)
        vis[c[i]] = true;
    int temp = 0;
    for (int i = 1; i <= n - 1; i++)
        for (int j = i + 1; j <= n; j++)
            if (vis[i] == vis[j] && !g[i][j])
            {
                lonely[i]++;
                lonely[j]++;
            }
    for (int i = 0; i < n; i++)
        temp = max(temp, lonely[i]);
    ans = min(ans, temp);
}

void dfs(int now, int t)
{
    if (now > n)
        return;
    if (t >= n / 2)
    {
        check(t);
        return;
    }
    c[t] = now;
    dfs(now + 1, t + 1);
    dfs(now + 1, t);
}

int main()
{
    //freopen("t.txt", "r", stdin);
    int a, b, maxa = 0;
    ans = 0x3f3f3f3f;
    while (scanf("%d", &a) != EOF)
    {
        maxa = max(a, maxa);
        scanf("%d", &n);
        for (int i = 0; i < n; i++)
        {
            scanf("%d", &b);
            g[a][b] = g[b][a] = true;
        }
    }
    n = maxa;
    dfs(1, 0);
    printf("%d\n", ans);
    return 0;
}