feat: Add solution for LeetCode problem 323

Author: WhiteHyun

number-of-connected-components-in-an-undirected-graph/WhiteHyun.swift

@@ -0,0 +1,40 @@
+//  
+//  323. Number of Connected Components in an Undirected Graph
+//  https://leetcode.com/problems/number-of-connected-components-in-an-undirected-graph/description/
+//  Dale-Study
+//  
+//  Created by WhiteHyun on 2024/07/06.
+//  
+
+final class Solution {
+  func countComponents(_ n: Int, _ edges: [[Int]]) -> Int {
+    var visited: Set<Int> = []
+    var count = 0
+
+    var graph: [Int: [Int]] = [:]
+
+    for edge in edges {
+      graph[edge[0], default: []].append(edge[1])
+      graph[edge[1], default: []].append(edge[0])
+    }
+
+    func dfs(_ node: Int) {
+      if visited.contains(node) {
+        return
+      }
+
+      visited.insert(node)
+
+      for nextNode in graph[node, default: []] {
+        dfs(nextNode)
+      }
+    }
+
+    for node in 0 ..< n where !visited.contains(node) {
+      count += 1
+      dfs(node)
+    }
+
+    return count
+  }
+}