Merge pull request kelvins#326 from Hardvan/floyd-warshall-java

Add Floyd Warshall algorithm in Java

Author: kelvins

README.md

@@ -135,8 +135,8 @@ In order to achieve greater coverage and encourage more people to contribute to
                 </a>
             </td>
             <td> <!-- Java -->
-                <a href="./CONTRIBUTING.md">
-                    <img align="center" height="25" src="./logos/github.svg" />
+                <a href="./src/java/FloydWarshall.java">
+                    <img align="center" height="25" src="./logos/java.svg" />
                 </a>
             </td>
             <td> <!-- Python -->

src/java/FloydWarshall.java

@@ -0,0 +1,66 @@
+/*
+ * Floyd-Warshall algorithm in Java
+ * All pairs shortest path algorithm
+ * Time Complexity:  O(n³)
+ * Space Complexity: O(n²)
+ */
+
+public class FloydWarshall {
+
+  public static void showMatrix(long[][] matriz, int nroVertices) {
+    for (int i = 0; i < nroVertices; i++) {
+      for (int j = 0; j < nroVertices; j++) {
+        if (matriz[i][j] < 10) {
+          System.out.print(" " + matriz[i][j] + " ");
+        } else {
+          System.out.print(matriz[i][j] + " ");
+        }
+      }
+
+      System.out.println();
+    }
+    System.out.println();
+  }
+
+  public static void main(String[] args) {
+    int nroVertices = 5;
+    long[][] matriz = {
+      {0, 2, 10, 5, 7},
+      {2, 0, 3, 3, 1},
+      {10, 3, 0, 1, 2},
+      {5, 3, 1, 0, Long.MAX_VALUE},
+      {7, 1, 2, 2, 0}
+    };
+
+    // Display the original matrix
+    System.out.println("Original matrix:");
+    showMatrix(matriz, nroVertices);
+
+    floydWarshall(matriz, nroVertices);
+
+    // Display the updated matrix
+    System.out.println("Updated matrix:");
+    showMatrix(matriz, nroVertices);
+
+    // Show all shortest paths
+    System.out.println();
+    for (int i = 0; i < nroVertices; i++) {
+      for (int x = 0; x < nroVertices; x++) {
+        System.out.println("Shortest distance from " + i + " to " + x + " = " + matriz[x][i] + ".");
+      }
+    }
+    System.out.println();
+  }
+
+  public static void floydWarshall(long[][] matriz, int n) {
+    for (int x = 0; x < n; x++) { // Intermediary vertex
+      for (int y = 0; y < n; y++) { // Origin vertex
+        for (int z = 0; z < n; z++) { // Destination vertex
+          if (matriz[y][z] > (matriz[y][x] + matriz[x][z])) {
+            matriz[y][z] = matriz[y][x] + matriz[x][z];
+          }
+        }
+      }
+    }
+  }
+}