最小点割集

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ACM模版
最小点割集

/* *  最小点割集(点连通度) */#define MAXN 100#define inf 1000000000int max_flow(int n, int mat[][MAXN], int source, int sink){    int v[MAXN], c[MAXN], p[MAXN], ret = 0, i, j;    for (; ;)    {        for (i = 0; i < n; i++)        {            v[i] = c[i] = 0;        }        for (c[source] = inf; ;)        {            for (j = -1, i = 0; i < n; i++)            {                if (!v[i] && c[i] && (j == -1 || c[i] > c[j]))                {                    j = i;                }            }            if (j < 0)            {                return ret;            }            if (j == sink)            {                break;            }            for (v[j] = 1, i = 0; i < n; i++)            {                if (mat[j][i] > c[i] && c[j] > c[i])                {                    c[i] = mat[j][i] < c[j] ? mat[j][i] : c[j], p[i] = j;                }            }        }        for (ret += j = c[i = sink]; i != source; i = p[i])        {            mat[p[i]][i] -= j, mat[i][p[i]] += j;        }    }}int min_vertex_cut(int n, int mat[][MAXN], int source, int sink, int *set){    int m0[MAXN][MAXN], m[MAXN][MAXN], i, j, k, ret = 0, last;    if (source == sink || mat[source][sink])    {        return -1;    }    for (i = 0; i < n + n; i++)    {        for (j = 0; j < n + n; j++)        {            m0[i][j] = 0;        }    }    for (i = 0; i < n; i++)    {        for (j = 0; j < n; j++)        {            if (mat[i][j])            {                m0[i][n + j] = inf;            }        }    }    for (i = 0; i < n; i++)    {        m0[n + i][i]=1;    }    for (i = 0; i < n + n; i++)    {        for (j = 0; j < n + n; j++)        {            m[i][j] = m0[i][j];        }    }    last = max_flow(n + n, m, source, n + sink);    for (k = 0; k < n && last; k++)    {        if (k != source && k != sink)        {            for (i = 0; i < n + n; i++)            {                for (j = 0; j < n + n; j++)                {                    m[i][j] = m0[i][j];                }            }            m[n+k][k] = 0;            if (max_flow(n + n, m, source, n + sink) < last)            {                set[ret++] = k;                m0[n+k][k] = 0;                last--;            }        }    }    return ret;}
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