Create FasterMaxflowButWeird.cpp

Graph/Flow/FasterMaxflowButWeird.cpp

@@ -0,0 +1,293 @@
+//....................................................................................//
+only works in planer graph!!
+//....................................................................................//
+#include <bits/stdc++.h>
+
+using namespace std;
+
+const int Nmax = 1200 + 7;
+const int Mmax = 100 * Nmax;
+const int NIL = -1;
+
+struct Edge
+{
+    int v;
+    int capacity;
+    int flow;
+
+    int urm;
+};
+
+Edge Graph[Mmax];
+int head[Nmax];
+
+long long excess[Nmax];
+int height[Nmax];
+bool active[Nmax];
+int pointer[Nmax];
+
+int countHeight[2 * Nmax];
+
+queue<int> Q;
+
+int N, M, countEdges;
+
+void addEdge(int u, int v, int cap1, int cap2)
+{
+    Graph[countEdges] = {v, cap1, 0, head[u]};
+    head[u] = countEdges++;
+
+    Graph[countEdges] = {u, cap2, 0, head[v]};
+    head[v] = countEdges++;
+}
+
+void enqueue(int v)
+{
+    if (!active[v] && excess[v] > 0)
+    {
+        active[v] = true;
+        Q.push(v);
+    }
+}
+
+void gap(int k)
+{
+    for (int i = 1; i <= N; ++i)
+    {
+        if (height[i] >= k)
+        {
+            countHeight[ height[i] ]--;
+            height[i] = max(height[i], N + 1);
+            countHeight[ height[i] ]++;
+
+            enqueue(i);
+        }
+    }
+}
+
+void push(int u, int p)
+{
+    int v = Graph[p].v;
+    long long delta = min(excess[u], (long long)(Graph[p].capacity - Graph[p].flow));
+
+    if (height[u] <= height[v] || delta == 0) return;
+
+    Graph[p].flow += delta;
+    Graph[p ^ 1].flow -= delta;
+
+    excess[u] -= delta;
+    excess[v] += delta;
+
+    enqueue(v);
+}
+
+void relabel(int v)
+{
+    countHeight[ height[v] ]--;
+
+    height[v] = 2 * N;
+
+    for (int p = head[v]; p != NIL; p = Graph[p].urm)
+    {
+        if (Graph[p].capacity - Graph[p].flow > 0)
+            height[v] = min(height[v], height[ Graph[p].v ] + 1);
+    }
+
+    countHeight[ height[v] ]++;
+
+    enqueue(v);
+}
+
+void discharge(int u)
+{
+    bool doneGap = 0;
+
+    while (excess[u] > 0)
+    {
+        if (countHeight[ height[u] ] == 1 && (doneGap == false))
+        {
+            gap(height[u]);
+
+            doneGap = true;
+            pointer[u] = NIL;
+        }
+
+        if (pointer[u] == NIL)
+        {
+            relabel(u);
+            pointer[u] = head[u];
+        }
+        else
+        {
+            int p = pointer[u];
+            int v = Graph[p].v;
+
+            if (height[u] >= height[v] + 1 && Graph[p].capacity > Graph[p].flow)
+                push(u, p);
+            else
+                pointer[u] = Graph[ pointer[u] ].urm;
+        }
+    }
+}
+
+void initPreflow(int S, int T)
+{
+    for (int i = 1; i <= N; ++i)
+    {
+        excess[i] = 0;
+        height[i] = 0;
+        pointer[i] = head[i];
+    }
+
+    height[S] = N;
+    active[S] = active[T] = true;
+
+    countHeight[N] = 1;
+    countHeight[0] = N - 1;
+
+    for (int p = head[S]; p != NIL; p = Graph[p].urm)
+    {
+        excess[S] += Graph[p].capacity;
+        push(S, p);
+    }
+}
+
+long long push_relabel(int S, int T)
+{
+    initPreflow(S, T);
+
+    while (Q.empty() == false)
+    {
+        int v = Q.front();
+        Q.pop();
+        active[v] = false;
+        discharge(v);
+    }
+
+    long long flow = 0;
+
+    for (int p = head[S]; p != NIL; p = Graph[p].urm)
+        flow += Graph[p].flow;
+
+    return flow;
+}
+
+int main()
+{
+    ///freopen("data.in", "r", stdin);
+
+    scanf("%d ", &N);
+    countEdges = 0;
+
+    scanf("%d ", &M);
+    int s, t ;
+    scanf("%d %d",&s, &t);
+    for (int i = 1; i <= N; ++i)
+        head[i] = NIL;
+
+    int x, y, c;
+
+    while (M--)
+    {
+        scanf("%d %d %d", &x, &y, &c);
+        addEdge(x, y, c, 0);
+    }
+
+    cout << push_relabel(s, t) << "\n";
+    return 0;
+}
+
+//....................................................................................//
+// One limitation of the HLPP implementation is that you can't recover the weights for the full flow - use Dinic's for this.
+//....................................................................................//
+template <int MAXN, class T = int> struct HLPP {
+    const T INF = numeric_limits<T>::max();
+    struct edge {
+        int to, rev;
+        T f;
+    };
+    int s = MAXN - 1, t = MAXN - 2;
+    vector<edge> adj[MAXN];
+    vector<int> lst[MAXN], gap[MAXN];
+    T excess[MAXN];
+    int highest, height[MAXN], cnt[MAXN], work;
+    void addEdge(int from, int to, int f, bool isDirected = true) {
+        adj[from].push_back({to, adj[to].size(), f});
+        adj[to].push_back({from, adj[from].size() - 1, isDirected ? 0 : f});
+    }
+    void updHeight(int v, int nh) {
+        work++;
+        if (height[v] != MAXN)
+            cnt[height[v]]--;
+        height[v] = nh;
+        if (nh == MAXN)
+            return;
+        cnt[nh]++, highest = nh;
+        gap[nh].push_back(v);
+        if (excess[v] > 0)
+            lst[nh].push_back(v);
+    }
+    void globalRelabel() {
+        work = 0;
+        fill(all(height), MAXN);
+        fill(all(cnt), 0);
+        for (int i = 0; i < highest; i++)
+            lst[i].clear(), gap[i].clear();
+        height[t] = 0;
+        queue<int> q({t});
+        while (!q.empty()) {
+            int v = q.front();
+            q.pop();
+            for (auto &e : adj[v])
+                if (height[e.to] == MAXN && adj[e.to][e.rev].f > 0)
+                    q.push(e.to), updHeight(e.to, height[v] + 1);
+            highest = height[v];
+        }
+    }
+    void push(int v, edge &e) {
+        if (excess[e.to] == 0)
+            lst[height[e.to]].push_back(e.to);
+        T df = min(excess[v], e.f);
+        e.f -= df, adj[e.to][e.rev].f += df;
+        excess[v] -= df, excess[e.to] += df;
+    }
+    void discharge(int v) {
+        int nh = MAXN;
+        for (auto &e : adj[v]) {
+            if (e.f > 0) {
+                if (height[v] == height[e.to] + 1) {
+                    push(v, e);
+                    if (excess[v] <= 0)
+                        return;
+                } else
+                    nh = min(nh, height[e.to] + 1);
+            }
+        }
+        if (cnt[height[v]] > 1)
+            updHeight(v, nh);
+        else {
+            for (int i = height[v]; i <= highest; i++) {
+                for (auto j : gap[i])
+                    updHeight(j, MAXN);
+                gap[i].clear();
+            }
+        }
+    }
+    T calc(int heur_n = MAXN) {
+        fill(all(excess), 0);
+        excess[s] = INF, excess[t] = -INF;
+        globalRelabel();
+        for (auto &e : adj[s])
+            push(s, e);
+        for (; highest >= 0; highest--) {
+            while (!lst[highest].empty()) {
+                int v = lst[highest].back();
+                lst[highest].pop_back();
+                discharge(v);
+                if (work > 4 * heur_n)
+                    globalRelabel();
+            }
+        }
+        return excess[t] + INF;
+    }
+};