POJ 1419

图的着色问题，转换为最大团问题，只有黑色不相邻就行。

void clique(int n, int* u, int mat[][MAXN], int size, int& max, int& bb, int* res, int* rr, int* c) {
    int i, j, vn, v[MAXN];
    if (n) {
        if (size + c[u[0]] <= max) return;
        for (i = 0; i < n + size - max && i < n; ++ i) {
            for (j = i + 1, vn = 0; j < n; ++ j)
                if (mat[u[i]][u[j]])
                    v[vn ++] = u[j];
            rr[size] = u[i];
            clique(vn, v, mat, size + 1, max, bb, res, rr, c);
            if (bb) return;
        }
    } else if (size > max) {
        max = size;
        for (i = 0; i < size; ++ i)
            res[i] = rr[i];
        bb = 1;
    }
}

int maxclique(int n, int mat[][MAXN], int *ret) {
    int max = 0, bb, c[MAXN], i, j;
    int vn, v[MAXN], rr[MAXN];
    for (c[i = n - 1] = 0; i >= 0; -- i) {
        for (vn = 0, j = i + 1; j < n; ++ j)
            if (mat[i][j])
                v[vn ++] = j;
        bb = 0;
        rr[0] = i;
        clique(vn, v, mat, 1, max, bb, ret, rr, c);
        c[i] = max;
    }
    return max;
}

int main()
{
    int n;
    int mat[MAXN][MAXN],ret[MAXN];
    SCF(n);
    while(n--)
    {
        int sum=0,a,b,m,h;
        SCF(m);SCF(h);
        SET(mat,1);SET(ret,0);
        F(j,h)
        {
            SCF(a);SCF(b);
            mat[a-1][b-1]=mat[b-1][a-1]=0;
        }
        PCFLN(maxclique(m,mat,ret));
        F(i,m)
        {
            if(ret[i]||i==0) PCF(ret[i]+1);
            else break;
            if(i!=m-1)
                printf(" ");
        }
        printf("\n");
    }

}