Number Of Connected Components In An Undirected Graph

Author: TonyKim9401

number-of-connected-components-in-an-undirected-graph/TonyKim9401.java

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+// TC: O(n + m)
+// n = the number of nodes, m = the number of edges
+// SC: O(n + m)
+// n, m are the each size of the 2 demension array 'edges'
+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) {
+            graph.get(edge[0]).add(edge[1]);
+            graph.get(edge[1]).add(edge[0]);
+        }
+
+        boolean[] visit = new boolean[n];
+        int count = 0;
+
+        for (int i = 0; i < n; i++) {
+            if (!visit[i]) {
+                count += 1;
+                dfs(i, graph, visit);
+            }
+        }
+        return count;
+    }
+
+    private void dfs(int node, List<List<Integer>> graph, boolean[] visit) {
+        visit[node] = true;
+        for (int neighbor : graph.get(node)) {
+            if (!visit[neighbor]) dfs(neighbor, graph, visit);
+        }
+    }
+}