Add Floyd-Warshall activity

src/main/java/com/packt/datastructuresandalg/lesson6/activity/floydwarshall/FloydWarshall.java

@@ -0,0 +1,35 @@
+package com.packt.datastructuresandalg.lesson6.activity.floydwarshall;
+
+import java.util.List;
+
+public class FloydWarshall {
+ int[][] adj;
+ int[][] path;
+
+ public FloydWarshall(int nodes) {
+ this.adj = new int[nodes][nodes];
+ this.path = new int[nodes][nodes];
+ for (int i = 0; i < adj.length; i++) {
+ for (int j = 0; j < adj[i].length; j++) {
+ if (i == j) {
+ this.adj[i][j] = 0;
+ this.path[i][j] = i;
+ } else {
+ this.adj[i][j] = Integer.MAX_VALUE;
+ this.path[i][j] = -1;
+ }
+ }
+ }
+ }
+
+ public void addEdge(int u, int v, int weight) {
+ if (weight < adj[u][v]) {
+ adj[u][v] = weight;
+ path[u][v] = u;
+ }
+ }
+
+ public List<Integer> path(int u, int v) { return null; }
+
+ public void run() { }
+}

src/main/java/com/packt/datastructuresandalg/lesson6/activity/floydwarshall/solution/FloydWarshall.java

@@ -0,0 +1,62 @@
+package com.packt.datastructuresandalg.lesson6.activity.floydwarshall.solution;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class FloydWarshall {
+ int[][] adj;
+ int[][] path;
+
+ public FloydWarshall(int nodes) {
+ this.adj = new int[nodes][nodes];
+ this.path = new int[nodes][nodes];
+ for (int i = 0; i < adj.length; i++) {
+ for (int j = 0; j < adj[i].length; j++) {
+ if (i == j) {
+ this.adj[i][j] = 0;
+ this.path[i][j] = i;
+ } else {
+ this.adj[i][j] = Integer.MAX_VALUE;
+ this.path[i][j] = -1;
+ }
+ }
+ }
+ }
+
+ public void addEdge(int u, int v, int weight) {
+ if (weight < adj[u][v]) {
+ adj[u][v] = weight;
+ path[u][v] = u;
+ }
+ }
+
+ public List<Integer> path(int u, int v) {
+ List<Integer> res = new ArrayList<>();
+ if (path[u][v] == -1)
+ return res;
+ int i = v;
+ while (u != i) {
+ res.add(0, i);
+ i = path[u][i];
+ }
+ res.add(0, u);
+ return res;
+ }
+
+ public void run() {
+ for (int k = 0; k < adj.length; k++) {
+ for (int i = 0; i < adj.length; i++) {
+ if (adj[i][k] >= Integer.MAX_VALUE)
+ continue;
+ for (int j = 0; j < adj.length; j++) {
+ if (adj[k][j] >= Integer.MAX_VALUE)
+ continue;
+ if (adj[i][k] + adj[k][j] < adj[i][j]) {
+ adj[i][j] = adj[i][k] + adj[k][j];
+ path[i][j] = path[k][j];
+ }
+ }
+ }
+ }
+ }
+}

src/test/java/com/packt/datastructuresandalg/lesson6/activity/floydwarshall/FloydWarshallTest.java

@@ -0,0 +1,28 @@
+package com.packt.datastructuresandalg.lesson6.activity.floydwarshall;
+
+import junit.framework.TestCase;
+
+import java.util.Arrays;
+
+public class FloydWarshallTest extends TestCase {
+ public void test() {
+ FloydWarshall f = new FloydWarshall(5);
+ f.addEdge(0, 1, 10);
+ f.addEdge(0, 3, 5);
+ f.addEdge(1, 3, 2);
+ f.addEdge(1, 2, 1);
+ f.addEdge(2, 4, 4);
+ f.addEdge(3, 1, 3);
+ f.addEdge(3, 2, 9);
+ f.addEdge(3, 4, 2);
+ f.addEdge(4, 2, 6);
+ f.run();
+
+ assertTrue(f.path(0, 0).equals(Arrays.asList(0)));
+ assertTrue(f.path(0, 1).equals(Arrays.asList(0, 3, 1)));
+ assertTrue(f.path(0, 2).equals(Arrays.asList(0, 3, 1, 2)));
+ assertTrue(f.path(0, 3).equals(Arrays.asList(0, 3)));
+ assertTrue(f.path(0, 4).equals(Arrays.asList(0, 3, 4)));
+ assertTrue(f.path(1, 4).equals(Arrays.asList(1, 3, 4)));
+ }
+}