Improved task 200

Author: javadev

README.md

@@ -69,7 +69,7 @@
 
 | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
 |-|-|-|-|-|-
-| 0200 |[Number of Islands](src/main/swift/g0101_0200/s0200_number_of_islands)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Linked_List, Recursion, Big_O_Time_O(N)_Space_O(1) | 4 | 89.47
+| 0200 |[Number of Islands](src/main/swift/g0101_0200/s0200_number_of_islands)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Depth_First_Search, Breadth_First_Search, Matrix, Union_Find, Big_O_Time_O(M\*N)_Space_O(M\*N) | 152 | 70.92
 
 #### Day 10 Dynamic Programming
 
@@ -337,7 +337,7 @@
 
 | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
 |-|-|-|-|-|-
-| 0200 |[Number of Islands](src/main/swift/g0101_0200/s0200_number_of_islands)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Linked_List, Recursion, Big_O_Time_O(N)_Space_O(1) | 4 | 89.47
+| 0200 |[Number of Islands](src/main/swift/g0101_0200/s0200_number_of_islands)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Depth_First_Search, Breadth_First_Search, Matrix, Union_Find, Big_O_Time_O(M\*N)_Space_O(M\*N) | 152 | 70.92
 
 #### Udemy Dynamic Programming
 
@@ -712,7 +712,7 @@
 
 | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
 |-|-|-|-|-|-
-| 0200 |[Number of Islands](src/main/swift/g0101_0200/s0200_number_of_islands)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Linked_List, Recursion, Big_O_Time_O(N)_Space_O(1) | 4 | 89.47
+| 0200 |[Number of Islands](src/main/swift/g0101_0200/s0200_number_of_islands)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Depth_First_Search, Breadth_First_Search, Matrix, Union_Find, Big_O_Time_O(M\*N)_Space_O(M\*N) | 152 | 70.92
 
 #### Day 7 Breadth First Search Depth First Search
 
@@ -1279,7 +1279,7 @@
 
 | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
 |-|-|-|-|-|-
-| 0200 |[Number of Islands](src/main/swift/g0101_0200/s0200_number_of_islands)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Linked_List, Recursion, Big_O_Time_O(N)_Space_O(1) | 4 | 89.47
+| 0200 |[Number of Islands](src/main/swift/g0101_0200/s0200_number_of_islands)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Depth_First_Search, Breadth_First_Search, Matrix, Union_Find, Big_O_Time_O(M\*N)_Space_O(M\*N) | 152 | 70.92
 
 #### Day 2 Matrix Related Problems
 
@@ -1432,7 +1432,7 @@
 | 0208 |[Implement Trie (Prefix Tree)](src/main/swift/g0201_0300/s0208_implement_trie_prefix_tree)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, String, Hash_Table, Design, Trie, Level_2_Day_16_Design, Udemy_Trie_and_Heap, Big_O_Time_O(word.length())_or_O(prefix.length())_Space_O(N) | 131 | 97.26
 | 0207 |[Course Schedule](src/main/swift/g0201_0300/s0207_course_schedule)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Graph, Topological_Sort, Big_O_Time_O(N)_Space_O(N) | 30 | 92.23
 | 0206 |[Reverse Linked List](src/main/swift/g0201_0300/s0206_reverse_linked_list)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Linked_List, Recursion, Data_Structure_I_Day_8_Linked_List, Algorithm_I_Day_10_Recursion_Backtracking, Level_1_Day_3_Linked_List, Udemy_Linked_List, Big_O_Time_O(N)_Space_O(1) | 4 | 89.47
-| 0200 |[Number of Islands](src/main/swift/g0101_0200/s0200_number_of_islands)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Linked_List, Recursion, Data_Structure_I_Day_8_Linked_List, Algorithm_I_Day_10_Recursion_Backtracking, Level_1_Day_3_Linked_List, Udemy_Linked_List, Big_O_Time_O(N)_Space_O(1) | 4 | 89.47
+| 0200 |[Number of Islands](src/main/swift/g0101_0200/s0200_number_of_islands)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Depth_First_Search, Breadth_First_Search, Matrix, Union_Find, Algorithm_II_Day_6_Breadth_First_Search_Depth_First_Search, Graph_Theory_I_Day_1_Matrix_Related_Problems, Level_1_Day_9_Graph/BFS/DFS, Udemy_Graph, Big_O_Time_O(M\*N)_Space_O(M\*N) | 152 | 70.92
 | 0198 |[House Robber](src/main/swift/g0101_0200/s0198_house_robber)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Algorithm_I_Day_12_Dynamic_Programming, Dynamic_Programming_I_Day_3, Level_2_Day_12_Dynamic_Programming, Udemy_Dynamic_Programming, Big_O_Time_O(n)_Space_O(n) | 0 | 100.00
 | 0189 |[Rotate Array](src/main/swift/g0101_0200/s0189_rotate_array)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Math, Two_Pointers, Algorithm_I_Day_2_Two_Pointers, Udemy_Arrays, Big_O_Time_O(n)_Space_O(1) | 118 | 91.36
 | 0169 |[Majority Element](src/main/swift/g0101_0200/s0169_majority_element)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Array, Hash_Table, Sorting, Counting, Divide_and_Conquer, Data_Structure_II_Day_1_Array, Udemy_Famous_Algorithm, Big_O_Time_O(n)_Space_O(1) | 38 | 96.59

src/main/swift/g0101_0200/s0200_number_of_islands/readme.md

@@ -45,34 +45,34 @@ An **island** is surrounded by water and is formed by connecting adjacent lands
 ## Solution
 
 ```swift
-/**
- * Definition for singly-linked list.
- * public class ListNode {
- *     public var val: Int
- *     public var next: ListNode?
- *     public init() { self.val = 0; self.next = nil; }
- *     public init(_ val: Int) { self.val = val; self.next = nil; }
- *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
- * }
- */
 class Solution {
-    func reverseList(_ head: ListNode?) -> ListNode? {
-        var prev: ListNode? = nil
-        var curr = head
-        var next = head?.next
-
-        while curr != nil {
-
-            // reverse the current nodes link
-            curr?.next = prev
-            
-            // update variables
-            prev = curr
-            curr = next
-            next = next?.next
+    func numIslands(_ grid: [[Character]]) -> Int {
+        var grid = grid
+        var islands = 0
+
+        if !grid.isEmpty && !grid[0].isEmpty {
+            for i in 0..<grid.count {
+                for j in 0..<grid[0].count {
+                    if grid[i][j] == "1" {
+                        dfs(&grid, i, j)
+                        islands += 1
+                    }
+                }
+            }
+        }
+        return islands
+    }
+
+    private func dfs(_ grid: inout [[Character]], _ x: Int, _ y: Int) {
+        if x < 0 || x >= grid.count || y < 0 || y >= grid[0].count || grid[x][y] != "1" {
+            return
         }
 
-        return prev
+        grid[x][y] = "x"
+        dfs(&grid, x + 1, y)
+        dfs(&grid, x - 1, y)
+        dfs(&grid, x, y + 1)
+        dfs(&grid, x, y - 1)
     }
 }
 ```

src/main/swift/g0501_0600/s0560_subarray_sum_equals_k/readme.md

@@ -30,20 +30,19 @@ Given an array of integers `nums` and an integer `k`, return _the total number o
 ```swift
 class Solution {
     func subarraySum(_ nums: [Int], _ k: Int) -> Int {
-       var result = 0
-    var dict = [Int: Int]()
-    dict[0] = 1
+        var result = 0
+        var dict = [Int: Int]()
+        dict[0] = 1
 
-    var sum = 0
-    for num in nums {
-        sum += num
-        if let val = dict[sum - k] {
-            result += val
+        var sum = 0
+        for num in nums {
+            sum += num
+            if let val = dict[sum - k] {
+                result += val
+            }
+            dict[sum, default: 0] += 1
         }
-        dict[sum, default: 0] += 1
-        }
-
-     return result 
+        return result 
     }
 }
 ```