【hdu 6214】Smallest Minimum Cut

【链接】 我是链接,点我呀:)

【题意】

求最小割中最少的边数。

【题解】

模板题

【代码】

const int INF = 1e9;
const int maxn = 1e3 + 7;
const int maxv = 2e4 + 5;
int head[maxv], cur[maxv], d[maxv], s, t, k, k1, sum, book[maxn];
int n, m;
void init()
{
    k = 0;
    memset(head, -1, sizeof(head));
}
struct node
{
    int v, w, next;
}edge[maxv];
void addEdge(int u, int v, int w)
{
    edge[k].v = v;
    edge[k].w = w;
    edge[k].next = head[u];
    head[u] = k++;
    edge[k].v = u;
    edge[k].w = 0;
    edge[k].next = head[v];
    head[v] = k++;

}
int Q[maxv];
int bfs()
{
    memset(d, 0, sizeof(d));
    d[s] = 1;
    int frnt = 0, rear = 0;
    Q[rear++] = s;
    while(frnt != rear)
    {
        int u = Q[frnt++];
        if(u == t) return 1;
        for(int i = head[u]; i != -1; i = edge[i].next)
        {
            int to = edge[i].v, w = edge[i].w;
            if(w && d[to] == 0)
            {
                d[to] = d[u] + 1;
                if(to == t) return 1;
                Q[rear++] = to;
            }
        }
    }
    return 0;
}
int dfs(int u, int maxflow)
{
    if(u == t || !maxflow) return maxflow;
    int ret = 0;
    for(int& i = cur[u]; i != -1; i = edge[i].next)
    {
        int to = edge[i].v, w = edge[i].w;
        if(w && d[to] == d[u]+1)
        {
            int f = dfs(to, min(maxflow-ret, w));
            edge[i].w -= f;
            edge[i^1].w += f;
            ret += f;
            if(ret == maxflow) return ret;
        }
    }
    return ret;
}
int Dinic()
{
    int ans = 0;
    while(bfs() == 1)
    {
        memcpy(cur, head, sizeof(head));
        ans += dfs(s, INF);
    }
    return ans;
}
int main()
{
    int _;
    scanf("%d", &_);
    while(_--)
    {
        int x, y, z;
        init();
        scanf("%d%d", &n, &m);
        scanf("%d%d", &s, &t);
        for(int i = 0; i < m; i++)
        {
            scanf("%d%d%d", &x, &y, &z);
            addEdge(x, y, z*(m+1)+1);
        }
        printf("%d\n", Dinic()%(m+1));
    }
    return 0;
}