Add 159

Author: trung-hn

Readme.md

@@ -38,6 +38,7 @@
 | 152 | Maximum Product Subarray | Medium | O(N) | O(N) | Dynamic Programming, Array | | |
 | 153 | Find Minimum in Rotated Sorted Array | Medium | O(logN) | O(1) | Binary Search | | |
 | 154 | Find Minimum in Rotated Sorted Array II | Hard | O(logN) | O(1) | Binary Search | | |
+| 159 | Longest Substring with At Most Two Distinct Characters | Medium | O(N) | O(1) | Premium, Hash Table, Two Pointers, String, Sliding Window | | |
 | 165 | Compare Version Numbers | Medium | O(N) | O(1) | String | | |
 | 171 | Excel Sheet Column Number | Easy | O(N) | O(1) | String | | |
 | 179 | Largest Number | Medium | O(NlogN) | O(1) | Sort | | |

src/159.py

@@ -0,0 +1,31 @@
+# TAGS: Premium, Hash Table, Two Pointers, String, Sliding Window
+
+class Solution:
+    # 360 ms, 5.36%. Time: O(N). Space; O(1)
+    def lengthOfLongestSubstringTwoDistinct(self, s: str) -> int:
+        def valid(counter):
+            return len(list(v for v, f in counter.items() if f > 0)) <= 2
+        
+        counter = collections.Counter()
+        left = ans = 0
+        for right, c in enumerate(s):
+            counter[c] += 1
+            if not valid(counter):
+                while not valid(counter):
+                    counter[s[left]] -= 1
+                    left += 1
+            ans = max(ans, right - left + 1)
+        return ans
+    
+    # 40 ms, 98.59%. Time: O(N). Space; O(1)
+    def lengthOfLongestSubstringTwoDistinct1(self, s: str) -> int:
+        counter = {}
+        left = ans = 0
+        for right, c in enumerate(s):
+            counter[c] = right
+            if len(counter) > 2:
+                left = min(counter.values())
+                del counter[s[left]]
+                left += 1
+            ans = max(ans, right - left + 1)
+        return ans

testcases/159

@@ -0,0 +1,6 @@
+"eceba"
+"ccaabbb"
+"a"
+""
+"aabaac"
+"baabaacaa"