KMP.py finally approved

Author: armanjscript

DataStructures/Section12/KMP.py

@@ -0,0 +1,40 @@
+#String matching by KMP algorithm
+
+def pfun(pattern):
+    n = len(pattern)
+    prefix_fun = [0]*(n)
+
+    k = 0
+    for q in range(2, n):
+        while k>0 and pattern[k + 1] != pattern[q]:
+            k = prefix_fun[k]
+        if pattern[k + 1] == pattern[q]:
+             k += 1
+        prefix_fun[q] = k
+    return prefix_fun
+
+
+def KMP_Matcher(text, pattern):
+    m = len(text)
+    n = len(pattern)
+    flag = False
+    text = '-' + text
+    pattern = '-' + pattern
+    prefix_fun = pfun(pattern)
+    q = 0
+
+    for i in range(1, m+1):
+        while q > 0 and pattern[q + 1] != text[i]:
+            q = prefix_fun[q]
+        if pattern[q + 1] == text[i]:
+            q += 1
+        if q == n:
+            print("Pattern occurs at positions ",i-n)     # print the index, where first match occurs.
+            flag = True
+            q = prefix_fun[q]
+    if not flag:
+        print('\nNo match found')
+
+
+#Output of KMP algorithm
+KMP_Matcher('aabaacaadaabaaba','aabaa')