hdu 1530 Maximum Clique

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=1530

题目分类：最大团问题 DP + DFS

代码：

#include<bits/stdc++.h>

using namespace std;
const int V=100;
int g[V][V], dp[V], stk[V][V], mx;
int dfs(int n, int ns, int dep)
{
    if (0 == ns)
    {
        if (dep > mx) mx = dep;
        return 1;
    }
    int i, j, k, p, cnt;
    for (i = 0; i < ns; i++)
    {
        k = stk[dep][i]; cnt = 0;
        if (dep + n - k <= mx) return 0;
        if (dep + dp[k] <= mx) return 0;
        for (j = i + 1; j < ns; j++)
        {
            p = stk[dep][j];
            if (g[k][p]) stk[dep + 1][cnt++] = p;
        }
        dfs(n, cnt, dep + 1);
    }
    return 1;
}

int clique(int n)
{
    int i, j, ns;
    for (mx = 0, i = n - 1; i >= 0; i--)
    {
        // vertex: 0 ~ n-1
        for (ns = 0, j = i + 1; j < n; j++)
        if (g[i][j]) stk[1][ ns++ ] = j;
        dfs(n, ns, 1); dp[i] = mx;
    }
    return mx;
}

int main()
{
    int n;
    while(scanf("%d",&n)&&n)
    {
        for(int i=0;i<n;i++)
        {
            for(int j=0;j<n;j++)
            {
                scanf("%d",&g[i][j]);
            }
        }
        int ans=clique(n);
        printf("%d
",ans);
    }
    return 0;
}