未加优化的ISAP算法

Author: Dev-XYS

Improved-Shortest-Augmenting-Path(Naive).cpp

@@ -0,0 +1,87 @@
+#include <cstdio>
+
+#define INF 1000000000
+#define VERTEX_COUNT 1000
+#define EDGE_COUNT 1000
+
+using namespace std;
+
+struct vertex
+{
+	int first, dis;
+}V[VERTEX_COUNT];
+
+struct edge
+{
+	int endp, next, flow;
+}E[EDGE_COUNT];
+
+int ec = 2, iec, ivc, src, sink;
+
+inline int min(int x, int y)
+{
+	return x < y ? x : y;
+}
+
+void add_edge(int u, int v, int f)
+{
+	E[ec].next = V[u].first;
+	V[u].first = ec;
+	E[ec].endp = v;
+	E[ec].flow = f;
+	ec++;
+}
+
+int DFS(int u, int curf)
+{
+	if (u == sink)
+	{
+		return curf;
+	}
+	int totalf = 0, mindis = INF;
+	for (int cur = V[u].first; cur != 0 && totalf < curf; cur = E[cur].next)
+	{
+		if (E[cur].flow > 0)
+		{
+			if (V[u].dis == V[E[cur].endp].dis + 1)
+			{
+				int t = DFS(E[cur].endp, min(curf - totalf, E[cur].flow));
+				E[cur].flow -= t;
+				E[cur ^ 1].flow += t;
+				totalf += t;
+			}
+			mindis = min(mindis, V[E[cur].endp].dis);
+		}
+	}
+	if (totalf == 0)
+	{
+		V[u].dis = mindis + 1;
+	}
+	return totalf;
+}
+
+int max_flow()
+{
+	int res = 0;
+	while (V[src].dis < ivc)
+	{
+		res += DFS(src, INF);
+	}
+	return res;
+}
+
+int main()
+{
+	int u, v, f;
+	scanf("%d%d", &iec, &ivc);
+	for (int i = 0; i < iec; i++)
+	{
+		scanf("%d%d%d", &u, &v, &f);
+		add_edge(u, v, f);
+		add_edge(v, u, 0);
+	}
+	src = 1;
+	sink = ivc;
+	printf("%d", max_flow());
+	return 0;
+}