340_Longest_Substring_with_At_Most_K_Distinct_Characters

Author: Partho Biswas

README.md

@@ -218,7 +218,7 @@ I have solved quite a number of problems from several topics. See the below tabl
 |09| [344. Reverse String](https://leetcode.com/problems/reverse-string/)| [Python](https://tinyurl.com/wu6rdaw/344_Reverse_String.py)|
 |10| [482. License Key Formatting](https://leetcode.com/problems/license-key-formatting/)| [Python](https://tinyurl.com/wu6rdaw/482_License_Key_Formatting.py)| |
 |11| [3. Longest Substring Without Repeating Characters](https://leetcode.com/problems/longest-substring-without-repeating-characters/)| [Python](https://tinyurl.com/wu6rdaw/3_Longest_Substring_Without_Repeating_Characters.py)| [Vid 1](https://tinyurl.com/tbwjwcf), [Vid 2](https://www.youtube.com/watch?v=3IETreEybaA) | Medium | 📌 Sliding window, Two pointer |
-|12| [340. Longest Substring with At Most K Distinct Characters](https://leetcode.com/problems/longest-substring-with-at-most-k-distinct-characters/)| [Python](https://tinyurl.com/wu6rdaw/340_Longest_Substring_with_At_Most_K_Distinct_Characters.py)| [Vid 1](https://tinyurl.com/t55ef99), [Art 1](https://tinyurl.com/vxumhku), [Art 2](https://tinyurl.com/ukyev7f) | Hard | 📌 Sliding window, Two pointer |
+|12| [340. Longest Substring with At Most K Distinct Characters](https://leetcode.com/problems/longest-substring-with-at-most-k-distinct-characters/)| [Python](https://tinyurl.com/wu6rdaw/340_Longest_Substring_with_At_Most_K_Distinct_Characters.py), [Swift](https://tinyurl.com/wuja3c4/340_Longest_Substring_with_At_Most_K_Distinct_Characters.swift) | [Vid 1](https://tinyurl.com/t55ef99), [Art 1](https://tinyurl.com/vxumhku), [Art 2](https://tinyurl.com/ukyev7f) | Hard | 📌 Sliding window, Two pointer |
 |13| [159. Longest Substring with At Most Two Distinct Characters](https://leetcode.com/problems/longest-substring-with-at-most-two-distinct-characters/)| [Python](https://tinyurl.com/wu6rdaw/159_Longest_Substring_with_At_Most_Two_Distinct_Characters.py)| [Vid 1](https://tinyurl.com/t55ef99) | Hard | 📌 Sliding window, Two pointer |
 |14| [424. Longest Repeating Character Replacement](https://leetcode.com/problems/longest-repeating-character-replacement/)| [Python](https://tinyurl.com/wu6rdaw/424_Longest_Repeating_Character_Replacement.py)| **[Vid 1](https://tinyurl.com/svyns7x)**, [Vid 2](https://tinyurl.com/rj3yt25), [Art 1](https://tinyurl.com/yx34cd9c), [Art 2](https://tinyurl.com/suxeoj3), [Art 3](https://tinyurl.com/slpeqnd), [Art 4](https://tinyurl.com/sje2no8) | Medium | 📌 Sliding window, Very important |
 |15| **[76. Minimum Window Substring](https://leetcode.com/problems/minimum-window-substring/)** | [Python](https://tinyurl.com/wu6rdaw/76_Minimum_Window_Substring.py)| **[Vid 1](https://tinyurl.com/tv8lqpa)**, **[Vid 2](https://tinyurl.com/v38h4j4)**, **[Vid 3](https://tinyurl.com/ss5ue49)**  | Hard | 📌 Sliding window, Very important |

leetcode.com/swift/DS_ALGO_PRAC.playground/Sources/swift/340_Longest_Substring_with_At_Most_K_Distinct_Characters.swift

@@ -0,0 +1,26 @@
+import Foundation
+class Solution {
+    func lengthOfLongestSubstringKDistinct(_ s: String, _ k: Int) -> Int {
+        guard k > 0 else {
+            return 0
+        }
+        var sArr = Array(s)
+        var counter = [Character:Int]()
+        var maxLen = 0
+        var (left, right) = (0, 0)
+        while right < sArr.count {
+            if counter[sArr[right]] != nil || counter.keys.count < k {
+                counter[sArr[right], default: 0] += 1
+                maxLen = max(maxLen, right - left + 1)
+                right += 1
+            } else {
+                counter[sArr[left], default: 0] -= 1
+                if counter[sArr[left]] == 0 {
+                    counter.removeValue(forKey: sArr[left])
+                }
+                left += 1
+            }
+        }
+        return maxLen
+    }
+}