Added Boyer Moore search and manacher algorithms

Strings/boyer_moore_search.py

@@ -0,0 +1,45 @@
+"""
+Pattern Finding.
+
+"""
+
+
+class BoyerMooreSearch:
+    def __init__(self, text, pattern):
+        self.text, self.pattern = text, pattern
+        self.textLen, self.patLen = len(text), len(pattern)
+
+    def match_in_pattern(self, char):
+        for i in range(self.patLen - 1, -1, -1):
+            if char == self.pattern[i]:
+                return i
+        return -1
+
+    def mismatch_in_text(self, currentPos):
+        for i in range(self.patLen - 1, -1, -1):
+            if self.pattern[i] != self.text[currentPos + i]:
+                return currentPos + i
+        return -1
+
+    def bad_character_heuristic(self):
+        positions = []
+        for i in range(self.textLen - self.patLen + 1):
+            mismatch_index = self.mismatch_in_text(i)
+            if mismatch_index == -1:
+                positions.append(i)
+            else:
+                match_index = self.match_in_pattern(self.text[mismatch_index])
+                i = (mismatch_index - match_index)
+        return positions
+
+
+text = "ABAABA"
+pattern = "AB"
+bms = BoyerMooreSearch(text, pattern)
+positions = bms.bad_character_heuristic()
+
+if len(positions) == 0:
+    print("No match found")
+else:
+    print("Pattern found in following positions: ")
+    print(positions)

Strings/manacher.py

@@ -0,0 +1,35 @@
+def palindromic_length(center, diff, string):
+    if (center - diff == -1 or center + diff == len(string)
+            or string[center - diff] != string[center + diff]):
+        return 0
+    return 1 + palindromic_length(center, diff + 1, string)
+
+
+def palindromic_string(input_string):
+    max_length = 0
+
+    new_input_string = ""
+    output_string = ""
+
+    for i in input_string[:len(input_string) - 1]:
+        new_input_string += i + "|"
+    new_input_string += input_string[-1]
+
+    for i in range(len(new_input_string)):
+
+        length = palindromic_length(i, 1, new_input_string)
+
+        if max_length < length:
+            max_length = length
+            start = i
+
+    for i in new_input_string[start - max_length:start + max_length + 1]:
+        if i != "|":
+            output_string += i
+
+    return output_string
+
+
+if __name__ == "__main__":
+    n = input()
+    print(palindromic_string(n))