merge mzuenni changes

1 files changed, 53 insertions, 98 deletions

diff --git a/graph/pushRelabel.cpp b/graph/pushRelabel.cpp
index 52ba8b1..904aec6 100644
--- a/graph/pushRelabel.cpp
+++ b/graph/pushRelabel.cpp
@@ -1,109 +1,64 @@
-constexpr ll inf = 1ll<<60;
-
 struct Edge {
-	int from, to;
+	int to, rev;
 	ll f, c;
 };
 
-vector<Edge> edges;
-vector<vector<int>> adj, llist;
-vector<int> height, ccount, que;
-vector<ll> excess;
-vector<list<int>> dlist;
-vector<list<int>::iterator> iter;
-int highest, highestActive;
-
-void addEdge(int from, int to, ll c) {
-	adj[from].push_back(sz(edges));
-	edges.push_back({from, to, 0, c});
-	adj[to].push_back(sz(edges));
-	edges.push_back({to, from, 0, 0});
-}
+vector<vector<Edge>> adj;
+vector<vector<int>> hs;
+vector<ll> ec;
+vector<int> cur, H;
 
-void globalRelabel(int n, int t) {
-	height.assign(n, n);
-	height[t] = 0;
-	ccount.assign(n, 0);
-	que.assign(n+1, 0);
-	int qh = 0, qt = 0;
-	for (que[qt++] = t; qh < qt;) {
-		int v = que[qh++], h = height[v] + 1;
-		for (int id : adj[v]) {
-			if (height[edges[id].to] == n && edges[id ^ 1].c - edges[id ^ 1].f > 0) {
-				ccount[height[edges[id].to] = h]++;
-				que[qt++] = edges[id].to;
-	}}}
-	llist.assign(n+1, {});
-	dlist.assign(n+1, {});
-	for (int v = 0; v < n; v++) {
-		if (height[v] < n) {
-			iter[v] = dlist[height[v]].insert(dlist[height[v]].begin(), v);
-			if (excess[v] > 0) llist[height[v]].push_back(v);
-	}}
-	highest = highestActive = height[que[qt - 1]];
+void addEdge(int u, int v, ll c) {
+    adj[u].push_back({v, (int)sz(adj[v]), 0, c});
+    adj[v].push_back({u, (int)sz(adj[u])-1, 0, 0});
 }
 
-void push(int v, int id) {
-	int u = edges[id].to;
-	ll df = min(excess[v], edges[id].c - edges[id].f);
-	edges[id].f += df;
-	edges[id^1].f -= df;
-	excess[v] -= df;
-	excess[u] += df;
-	if (0 < excess[u] && excess[u] <= df) llist[height[u]].push_back(u);
+void addFlow(Edge& e, ll f) {
+	if (ec[e.to] == 0 && f > 0)
+		hs[H[e.to]].push_back(e.to);
+	e.f += f;
+	adj[e.to][e.rev].f -= f;
+	ec[e.to] += f;
+	ec[adj[e.to][e.rev].to] -= f;
 }
 
-void discharge(int n, int v) {
-	int nh = n;
-	for (int id : adj[v]) {
-		if (edges[id].c - edges[id].f > 0) {
-			if (height[v] == height[edges[id].to] + 1) {
-				push(v, id);
-				if (!excess[v]) return;
-			} else {
-				nh = min(nh, height[edges[id].to] + 1);
-	}}}
-	int h = height[v];
-	if (ccount[h] == 1) {
-		for (int i = h; i <= highest; i++) {
-			for (auto p : dlist[i]) --ccount[height[p]], height[p] = n;
-			dlist[i].clear();
-		}
-		highest = h - 1;
-	} else {
-		--ccount[h], iter[v] = dlist[h].erase(iter[v]), height[v] = nh;
-		if (nh == n) return;
-		++ccount[nh], iter[v] = dlist[nh].insert(dlist[nh].begin(), v);
-		highest = max(highest, highestActive = nh);
-		llist[nh].push_back(v);
-}}
-
 ll maxFlow(int s, int t) {
 	int n = sz(adj);
-	llist.assign(n + 1, {});
-	dlist.assign(n + 1, {});
-	highestActive = highest = 0;
-	height.assign(n, 0);
-	height[s] = n;
-	iter.resize(n);
-	for (int v = 0; v < n; v++) {
-		if (v != s) iter[v] = dlist[height[v]].insert(dlist[height[v]].begin(), v);
-	}
-	ccount.assign(n, 0);
-	ccount[0] = n-1;
-	excess.assign(n, 0);
-	excess[s] = inf;
-	excess[t] = -inf;
-	for (int id : adj[s]) push(s, id);
-	globalRelabel(n, t);
-	while (highestActive >= 0) {
-		if (llist[highestActive].empty()) {
-			highestActive--;
-			continue;
-		}
-		int v = llist[highestActive].back();
-		llist[highestActive].pop_back();
-		discharge(n, v);
-	}
-	return excess[t] + inf;
-}
+	hs.assign(2*n, {});
+	ec.assign(n, 0);
+	cur.assign(n, 0);
+	H.assign(n, 0);
+	H[s] = n;
+	ec[t] = 1;//never set t to active...
+	vector<int> co(2*n);
+	co[0] = n - 1;
+	for (Edge& e : adj[s]) addFlow(e, e.c);
+	for (int hi = 0;;) {
+		while (hs[hi].empty()) if (!hi--) return -ec[s];
+		int v = hs[hi].back();
+		hs[hi].pop_back();
+		while (ec[v] > 0) {
+			if (cur[v] == sz(adj[v])) {
+				H[v] = 2*n;
+				for (int i = 0; i < sz(adj[v]); i++) {
+					Edge& e = adj[v][i];
+					if (e.c - e.f > 0 &&
+					    H[v] > H[e.to] + 1) {
+						H[v] = H[e.to] + 1;
+						cur[v] = i;
+				}}
+				co[H[v]]++;
+				if (!--co[hi] && hi < n) {
+					for (int i = 0; i < n; i++) {
+						if (hi < H[i] && H[i] < n) {
+							co[H[i]]--;
+							H[i] = n + 1;
+				}}}
+				hi = H[v];
+			} else {
+				Edge& e = adj[v][cur[v]];
+				if (e.c - e.f > 0 && H[v] == H[e.to] + 1) {
+					addFlow(adj[v][cur[v]], min(ec[v], e.c - e.f));
+				} else {
+					cur[v]++;
+}}}}}