improves vertex validation in BFS and DFS

Author: kevin-wayne

src/main/java/edu/princeton/cs/algs4/BreadthFirstDirectedPaths.java

@@ -185,11 +185,9 @@ private void validateVertices(Iterable<Integer> vertices) {
         int V = marked.length;
         for (Integer v : vertices) {
             if (v == null) {
-                throw new IllegalArgumentException("vertex " + v + " is null");
-            }
-            if (v < 0 || v >= V) {
-                throw new IllegalArgumentException("vertex " + v + " is not between 0 and " + (V-1));
+                throw new IllegalArgumentException("vertex is null");
             }
+            validateVertex(v);
         }
     }
 

src/main/java/edu/princeton/cs/algs4/BreadthFirstPaths.java

@@ -248,11 +248,9 @@ private void validateVertices(Iterable<Integer> vertices) {
         int V = marked.length;
         for (Integer v : vertices) {
             if (v == null) {
-                throw new IllegalArgumentException("vertex " + v + " is null");
-            }
-            if (v < 0 || v >= V) {
-                throw new IllegalArgumentException("vertex " + v + " is not between 0 and " + (V-1));
+                throw new IllegalArgumentException("vertex is null");
             }
+            validateVertex(v);
         }
     }
 

src/main/java/edu/princeton/cs/algs4/DirectedDFS.java

@@ -121,11 +121,9 @@ private void validateVertices(Iterable<Integer> vertices) {
         int V = marked.length;
         for (Integer v : vertices) {
             if (v == null) {
-                throw new IllegalArgumentException("vertex " + v + " is null");
-            }
-            if (v < 0 || v >= V) {
-                throw new IllegalArgumentException("vertex " + v + " is not between 0 and " + (V-1));
+                throw new IllegalArgumentException("vertex is null");
             }
+            validateVertex(v);
         }
     }