src: Add and use default MinPQ.addOrChangePriority

Author: kevinlin1

src/graphs/shortestpaths/AStarSolver.java

@@ -43,11 +43,7 @@ public AStarSolver(AStarGraph<V> graph, V start, V goal) {
                     edgeTo.put(to, e);
                     distTo.put(to, newDist);
                     double priority = newDist + graph.estimatedDistance(to, goal);
-                    if (pq.contains(to)) {
-                        pq.changePriority(to, priority);
-                    } else {
-                        pq.add(to, priority);
-                    }
+                    pq.addOrChangePriority(to, priority);
                 }
             }
         }

src/graphs/shortestpaths/DijkstraSolver.java

@@ -39,11 +39,7 @@ public DijkstraSolver(Graph<V> graph, V start) {
                 if (newDist < oldDist) {
                     edgeTo.put(to, e);
                     distTo.put(to, newDist);
-                    if (pq.contains(to)) {
-                        pq.changePriority(to, newDist);
-                    } else {
-                        pq.add(to, newDist);
-                    }
+                    pq.addOrChangePriority(to, newDist);
                 }
             }
         }

src/minpq/MinPQ.java

@@ -22,6 +22,21 @@ public interface MinPQ<E> {
      */
     void add(E element, double priority);
 
+    /**
+     * Adds an element with the given priority value if it is not already present. Otherwise, updates the priority value
+     * of the existing element.
+     *
+     * @param element  the element to add or update.
+     * @param priority the priority value for the element.
+     */
+    default void addOrChangePriority(E element, double priority) {
+        if (!contains(element)) {
+            add(element, priority);
+        } else {
+            changePriority(element, priority);
+        }
+    }
+
     /**
      * Returns true if the given element is in this priority queue.
      *