模板_Dinic算法

const int inf = 0x3f3f3f3f;
const int MX = 105;
const int MXE = 4 * MX * MX;
struct MaxFlow {
    struct Edge {
        int v, w, nxt;
    } edge[MXE];
    int tot, num, s, t;
    int head[MX];
    void init() {
        memset(head, -1, sizeof(head));
        tot = 0;
    }
    void add(int u, int v, int w) {
        edge[tot].v = v;
        edge[tot].w = w;
        edge[tot].nxt = head[u];
        head[u] = tot++;

        edge[tot].v = u;
        edge[tot].w = 0;
        edge[tot].nxt = head[v];
        head[v] = tot++;
    }

    int  d[MX], vis[MX], gap[MX];
    void bfs() {
        memset(d, 0, sizeof(d));
        memset(gap, 0, sizeof(gap));
        memset(vis, 0, sizeof(vis));
        queue<int>q;
        q.push(t);
        vis[t] = 1;
        while (!q.empty()) {
            int u = q.front();
            q.pop();
            for (int i = head[u]; ~i; i = edge[i].nxt) {
                int v = edge[i].v;
                if (!vis[v]) {
                    d[v] = d[u] + 1;
                    gap[d[v]]++;
                    q.push(v);
                    vis[v] = 1;
                }
            }
        }
    }

    int last[MX];
    int dfs(int u, int f) {
        if (u == t) return f;
        int sap = 0;
        for (int i = last[u]; ~i; i = edge[i].nxt) {
            int v = edge[i].v;
            if (edge[i].w > 0 && d[u] == d[v] + 1) {
                last[u] = i;
                int tmp = dfs(v, min(f - sap, edge[i].w));
                edge[i].w -= tmp;
                edge[i ^ 1].w += tmp;
                sap += tmp;
                if (sap == f) return sap;
            }
        }
        if (d[s] >= num) return sap;
        if (!(--gap[d[u]])) d[s] = num;
        ++gap[++d[u]];
        last[u] = head[u];
        return sap;
    }

    int solve(int st, int ed, int n) {
        int flow = 0;
        num = n;
        s = st;
        t = ed;
        bfs();
        memcpy(last, head, sizeof(head));
        while (d[s] < num) flow += dfs(s, inf);
        return flow;
    }
} F;