style: include SUI_CONTAINS_BEFORE_ADD

Author: vil02

spotbugs-exclude.xml

@@ -225,9 +225,6 @@
     <Match>
         <Bug pattern="IMC_IMMATURE_CLASS_BAD_SERIALVERSIONUID" />
     </Match>
-    <Match>
-        <Bug pattern="SUI_CONTAINS_BEFORE_ADD" />
-    </Match>
     <Match>
         <Bug pattern="DRE_DECLARED_RUNTIME_EXCEPTION" />
     </Match>

src/main/java/com/thealgorithms/datastructures/graphs/ConnectedComponent.java

@@ -81,8 +81,7 @@ public int countGraphs() {
         Set<Node> markedNodes = new HashSet<Node>();
 
         for (Node n : nodeList) {
-            if (!markedNodes.contains(n)) {
-                markedNodes.add(n);
+            if (markedNodes.add(n)) {
                 markedNodes.addAll(depthFirstSearch(n, new ArrayList<Node>()));
                 count++;
             }