#161 is started

Author: Hamid Gasmi

5-string-processing-and-pattern-matching-algorithms/2-burrows-wheeler-suffix-arrays/bwmatching.py

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+# python3
+import sys
+
+
+def PreprocessBWT(bwt):
+  """
+  Preprocess the Burrows-Wheeler Transform bwt of some text
+  and compute as a result:
+    * starts - for each character C in bwt, starts[C] is the first position 
+        of this character in the sorted array of 
+        all characters of the text.
+    * occ_count_before - for each character C in bwt and each position P in bwt,
+        occ_count_before[C][P] is the number of occurrences of character C in bwt
+        from position 0 to position P inclusive.
+  """
+  # Implement this function yourself
+  pass
+
+
+def CountOccurrences(pattern, bwt, starts, occ_counts_before):
+  """
+  Compute the number of occurrences of string pattern in the text
+  given only Burrows-Wheeler Transform bwt of the text and additional
+  information we get from the preprocessing stage - starts and occ_counts_before.
+  """
+  # Implement this function yourself
+  return 0
+     
+
+
+if __name__ == '__main__':
+  bwt = sys.stdin.readline().strip()
+  pattern_count = int(sys.stdin.readline().strip())
+  patterns = sys.stdin.readline().strip().split()
+  # Preprocess the BWT once to get starts and occ_count_before.
+  # For each pattern, we will then use these precomputed values and
+  # spend only O(|pattern|) to find all occurrences of the pattern
+  # in the text instead of O(|pattern| + |text|).  
+  starts, occ_counts_before = PreprocessBWT(bwt)
+  occurrence_counts = []
+  for pattern in patterns:
+    occurrence_counts.append(CountOccurrences(pattern, bwt, starts, occ_counts_before))
+  print(' '.join(map(str, occurrence_counts)))

5-string-processing-and-pattern-matching-algorithms/2-burrows-wheeler-suffix-arrays/bwmatching_tests/01

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+AGGGAA$
+1
+GA

5-string-processing-and-pattern-matching-algorithms/2-burrows-wheeler-suffix-arrays/bwmatching_tests/01e

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+3

5-string-processing-and-pattern-matching-algorithms/2-burrows-wheeler-suffix-arrays/bwmatching_tests/02

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+ATT$AA
+2
+ATA A

5-string-processing-and-pattern-matching-algorithms/2-burrows-wheeler-suffix-arrays/bwmatching_tests/02e

@@ -0,0 +1 @@
+2 3

5-string-processing-and-pattern-matching-algorithms/2-burrows-wheeler-suffix-arrays/bwmatching_tests/03

@@ -0,0 +1,3 @@
+AT$TCTATG
+2
+TCT TATG

5-string-processing-and-pattern-matching-algorithms/2-burrows-wheeler-suffix-arrays/bwmatching_tests/03e

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+0 0