Rabin-Karp.py finally approved

Author: armanjscript

DataStructures/Section12/Rabin-Karp.py

@@ -0,0 +1,44 @@
+#String matching by Rabin-Kap algorithm
+
+def generate_hash(text, pattern):
+    ord_text = [ord(i) for i in text]
+    ord_pattern = [ord(i) for i in pattern]
+    len_text = len(text)
+    len_pattern = len(pattern)
+    len_hash_array = len_text - len_pattern + 1
+    hash_text = [0]*(len_hash_array)
+    hash_pattern = sum(ord_pattern)
+
+    for i in range(0, len_hash_array):
+        if i == 0:
+            hash_text[i] = sum(ord_text[:len_pattern])
+        else:
+            hash_text[i] = ((hash_text[i - 1] - ord_text[i - 1]) + ord_text[i+len_pattern-1])
+    return [hash_text, hash_pattern]
+
+
+def Rabin_Karp_Matcher(text, pattern):
+    text = str(text) 
+    pattern = str(pattern)
+    hash_text, hash_pattern = generate_hash(text, pattern)
+    len_text = len(text) 
+    len_pattern = len(pattern)
+    flag = False
+    for i in range(len(hash_text)):
+        if hash_text[i] == hash_pattern:
+            count = 0
+            for j in range(len_pattern):
+                if pattern[j] == text[i + j]:
+                    count+=1
+                else:
+                    break
+            if count == len_pattern:
+                flag = True
+                print("\nPattern occurs at index ", i)
+    if not flag:
+        print("Pattern is not at all present in the text")
+
+
+#Output of Rabin-Karp
+Rabin_Karp_Matcher("101110000011010010101101","1011")
+Rabin_Karp_Matcher("ABBACCADABBACCEDF","ACCE")