solve number of connected components in an undirected graph

Author: sora0319

number-of-connected-components-in-an-undirected-graph/sora0319.java

@@ -0,0 +1,37 @@
+public class Solution {
+    public int countComponents(int n, int[][] edges) {
+        List<List<Integer>> graph = new ArrayList<>();
+        for (int i = 0; i < n; i++) {
+            graph.add(new ArrayList<>());
+        }
+        for (int[] edge : edges) {
+            int node = edge[0];
+            int adj = edge[1];
+            graph.get(node).add(adj);
+            graph.get(adj).add(node);
+        }
+
+        int count = 0;
+        Set<Integer> visited = new HashSet<>();
+        for (int node = 0; node < n; node++) {
+            if (visited.contains(node)) {
+                continue;
+            }
+            count++;
+            Deque<Integer> queue = new ArrayDeque<>();
+            queue.push(node);
+            while (!queue.isEmpty()) {
+                int cur = queue.pop();
+                if (visited.contains(cur)) continue;
+                visited.add(cur);
+                for (int g : graph.get(cur)) {
+                    if (!visited.contains(g)) {
+                        queue.push(g);
+                    }
+                }
+            }
+        }
+        return count;
+    }
+}
+