Create count-substrings-that-satisfy-k-constraint-i.py

Author: kamyu104

Python/count-substrings-that-satisfy-k-constraint-i.py

@@ -0,0 +1,19 @@
+# Time:  O(n)
+# Space: O(1)
+
+# two pointers, sliding window
+class Solution(object):
+    def countKConstraintSubstrings(self, s, k):
+        """
+        :type s: str
+        :type k: int
+        :rtype: int
+        """
+        result = cnt = left = 0
+        for right in xrange(len(s)):
+            cnt += int(s[right] == '1')
+            while not (cnt <= k or (right-left+1)-cnt <= k):
+                cnt -= int(s[left] == '1')
+                left += 1
+            result += right-left+1
+        return result