Merge pull request #108 from patniharshit/master

add Edmund Karp in java

Java/EdmundKarp.java

@@ -0,0 +1,68 @@
+import java.util.*;
+import java.io.*;
+
+public class Main {
+	private static final int MAX_V = 40; // enough for sample graph in Figure 4.24/4.25/4.26
+	private static final int INF = 1000000000;
+
+	// we need these global variables
+	private static int[][] res = new int[MAX_V][]; // define MAX_V appropriately
+	private static int mf, f, s, t;
+	private static Vector < Integer > p = new Vector < Integer > ();
+
+	private static void augment(int v, int minEdge) { // traverse the BFS spanning tree as in print_path (section 4.3)
+		if (v == s) { f = minEdge; return; } // reach the source, record minEdge in a global variable `f'
+		else if (p.get(v) != -1) { augment(p.get(v), Math.min(minEdge, res[p.get(v)][v])); // recursive call
+			res[p.get(v)][v] -= f; res[v][p.get(v)] += f; } // alter residual capacities
+	}
+
+	public static void main(String[] args) throws Exception {
+		int V, k, vertex, weight;
+
+		Scanner sc = new Scanner(System.in);
+
+		V = sc.nextInt();
+		s = sc.nextInt();
+		t = sc.nextInt();
+
+		for (int i = 0; i < V; i++) {
+			res[i] = new int[MAX_V];
+			k = sc.nextInt();
+			for (int j = 0; j < k; j++) {
+				vertex = sc.nextInt();
+				weight = sc.nextInt();
+				res[i][vertex] = weight;
+			}
+		}
+
+		mf = 0;
+		while (true) { // run O(VE^2) Edmonds Karp to solve the Max Flow problem
+			f = 0;
+
+			// run BFS, please examine parts of the BFS code that is different than in Section 4.3
+			Queue < Integer > q = new LinkedList < Integer > ();
+			Vector < Integer > dist = new Vector < Integer > ();
+			dist.addAll(Collections.nCopies(V, INF)); // #define INF 2000000000
+			q.offer(s);
+			dist.set(s, 0);
+			p.clear();
+			p.addAll(Collections.nCopies(V, -1)); // (we have to record the BFS spanning tree)
+			while (!q.isEmpty()) {                // (we need the shortest path from s to t!)
+				int u = q.poll();
+				if (u == t) break; // immediately stop BFS if we already reach sink t
+				for (int v = 0; v < MAX_V; v++) // note: enumerating neighbors with AdjMatrix is `slow'
+					if (res[u][v] > 0 && dist.get(v) == INF) { // res[u][v] can change!
+						dist.set(v, dist.get(u) + 1);
+						q.offer(v);
+						p.set(v, u); // parent of vertex v is vertex u
+					}
+			}
+
+			augment(t, INF); // find the min edge weight `f' along this path, if any
+			if (f == 0) break; // if we cannot send any more flow (`f' = 0), terminate the loop
+			mf += f; // we can still send a flow, increase the max flow!
+		}
+
+		System.out.printf("%d\n", mf); // this is the max flow value of this flow graph
+	}
+}

README.md

@@ -26,7 +26,7 @@ Reference purposes .
 23. Pollard Rho Integer Factorization [cpp](https://github.com/saru95/DSA/blob/master/PRB.cpp) [python](https://github.com/saru95/DSA/blob/master/Python/PRB.py)
 24. Binary Indexed Trees / BIT [cpp](https://github.com/saru95/DSA/blob/master/BIT.cpp) [python](https://github.com/DravitLochan/DSA/blob/master/Python/BIT.py)
 25. Square Root Decomposition [cpp](https://github.com/saru95/DSA/blob/master/SRD.cpp)
-26. Ford-Fulkerson Algorithm for Maximum Flow (BFS)/ Edmonds Karp Algorithm [cpp](https://github.com/saru95/DSA/blob/master/FFA.cpp)
+26. Ford-Fulkerson Algorithm for Maximum Flow (BFS)/ Edmonds Karp Algorithm [cpp](https://github.com/saru95/DSA/blob/master/FFA.cpp) [java](https://github.com/saru95/DSA/pull/108/files)
 27. Miller Rabin Primality Test [cpp](https://github.com/saru95/DSA/blob/master/MRPT.cpp) [python] (https://github.com/saru95/DSA/blob/master/Python/MRPT.py)
 28. Fibonacci Numbers using fast doubling [cpp](https://github.com/saru95/DSA/blob/master/fastdoublingfibo.cpp) [python](https://github.com/saru95/DSA/blob/master/Python/Fourier-Doubling.py) [java](https://github.com/saru95/DSA/blob/master/Java/FastDoublingFibo.java)
 29. Generating Non-Fibonacci Numbers [cpp](https://github.com/saru95/DSA/blob/master/NonFibo.cpp) [python](https://github.com/saru95/DSA/blob/master/Python/nNonFib.py)