Merge pull request #335 from durid17/Z-Algorithm

Z_Algorithm

Author: prabhupant

algorithms/dynamic_programming/Z_Algorithm.py

@@ -0,0 +1,30 @@
+class Z_Algorithm():
+    """
+        return all occurences of string s in text, returns its indexes starting from zero
+        delimeter should be charachter which will not occur neither is S nor in text
+        by default its '$'
+    """
+    @staticmethod
+    def find_occurrences(s:str , text:str , delimeter = '$'):
+        return Z_Algorithm.z_function(s + delimeter + text , len(s))
+    
+    @staticmethod
+    def z_function(text:str , size:int):
+        l = 0
+        r = 0
+        z = [0] * len(text)
+        for i in range(1 , len(text)):
+            if i <= r:
+                z[i] = min(r - i + 1 , z[i - l])
+            while i + z[i] < len(text) and text[z[i]] == text[i + z[i]]:
+                z[i] += 1
+            
+            if i + z[i] - 1 > r:
+                l = i
+                r = i + z[i] - 1
+        
+        res = []
+        for i in range(size , len(text)):
+            if z[i] == size:
+                res.append(i - size - 1)
+        return res