Create find-pattern-in-infinite-stream-i.py

Author: kamyu104

Python/find-pattern-in-infinite-stream-i.py

@@ -0,0 +1,39 @@
+# Time:  O(p + n)
+# Space: O(p)
+
+class InfiniteStream:
+    def next(self):
+        pass
+
+
+# kmp
+class Solution(object):
+    def findPattern(self, stream, pattern):
+        """
+        :type stream: InfiniteStream
+        :type pattern: List[int]
+        :rtype: int
+        """
+        def getPrefix(pattern):
+            prefix = [-1]*len(pattern)
+            j = -1
+            for i in xrange(1, len(pattern)):
+                while j+1 > 0 and pattern[j+1] != pattern[i]:
+                    j = prefix[j]
+                if pattern[j+1] == pattern[i]:
+                    j += 1
+                prefix[i] = j
+            return prefix
+
+        prefix = getPrefix(pattern)
+        i = j = -1
+        while True:
+            d = stream.next()
+            i += 1
+            while j+1 > 0 and pattern[j+1] != d:
+                j = prefix[j]
+            if pattern[j+1] == d:
+                j += 1
+            if j+1 == len(pattern):
+                return i-j
+        return -1