Create substrings-of-size-three-with-distinct-characters.py

Author: kamyu104

Python/substrings-of-size-three-with-distinct-characters.py

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+# Time:  O(n)
+# Space: O(1)
+
+import collections
+
+
+class Solution(object):
+    def countGoodSubstrings(self, s):
+        """
+        :type s: str
+        :rtype: int
+        """
+        K = 3
+
+        result = 0
+        count = collections.Counter()
+        for i in xrange(len(s)):
+            if i >= K:
+                count[s[i-K]] -= 1
+                if not count[s[i-K]]:
+                    del count[s[i-K]]
+            count[s[i]] += 1
+            if len(count) == K:
+                result += 1
+        return result