无向图最小割

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ACM模版
无向图最小割

/* *  INIT: 初始化邻接矩阵g[][] *  CALL: res = mincut(n); *  注: Stoer-Wagner Minimum Cut; *  找边的最小集合，若其被删去则图变得不连通（我们把这种形式称为最小割问题） */#define typec int               //  type of resconst typec inf = 0x3f3f3f3f;   //  max of resconst typec maxw = 1000;        //  maximum edge weightconst typec V = 10010;typec g[V][V], w[V];int a[V], v[V], na[V];typec minCut(int n){    int i, j, pv, zj;    typec best = maxw * n * n;    for (i = 0; i < n; i++)    {        v[i] = i;   //  vertex: 0 ~ n-1    }    while (n > 1)    {        for (a[v[0]] = 1, i = 1; i < n; i++)        {            a[v[i]] = 0;            na[i - 1] = i;            w[i] = g[v[0]][v[i]];        }        for (pv = v[0], i = 1; i < n; i++)        {            for (zj = -1, j = 1; j < n; j++)            {                if (!a[v[j]] && (zj < 0 || w[j] > w[zj]))                {                    zj = j;                }            }            a[v[zj]] = 1;            if (i == n - 1)            {                if (best > w[zj])                {                    best = w[zj];                }                for (i = 0; i < n; i++)                {                    g[v[i]][pv] = g[pv][v[i]] += g[v[zj]][v[i]];                }                v[zj] = v[--n];                break;            }            pv = v[zj];            for (j = 1; j < n; j++)            {                if(!a[v[j]])                {                    w[j] += g[v[zj]][v[j]];                }            }        }    }    return best;}
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