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```#!/usr/bin/env python3.2

import numpy as np

def longest_common_substring(src, dst) :
c = np.zeros((len(src), len(dst)), dtype=np.int)
z = 0
src_m = None
dst_m = None
for i in range(len(src)) :
for j in range(len(dst)) :
if src[i] == dst[j] :
if i == 0 or j == 0 :
c[i,j] = 1
else :
c[i, j] = c[i-1, j-1] + 1
if c[i, j] > z :
z = c[i, j]
if c[i, j] == z :
src_m = (i-z+1, i+1)
dst_m = (j-z+1, j+1)
else :
c[i, j] = 0
return src_m, dst_m

>>> a = """Lorem ipsum dolor sit amet consectetur adipiscing
elit Ut id nisl quis lacus lobortis egestas id nec turpis""".split()
>>> b = """Lorem ipsum lobortis dolor sit adipiscing elit dolor
amet consectetur Ut id nisl quis lacus egestas id nec turpis""".split()
>>> src_m, dst_m = longest_common_substring(a, b)
>>> print(src_m[0], src_m[1])
8 13
>>> print(a[src_m[0]:src_m[1]])
['Ut', 'id', 'nisl', 'quis', 'lacus']
>>> print(dst_m[0], dst_m[1])
10 15
>>> print(b[dst_m[0]:dst_m[1]])
['Ut', 'id', 'nisl', 'quis', 'lacus']
```

#### Diff to Previous Revision

```--- revision 3 2013-02-19 09:53:47
+++ revision 4 2013-03-05 19:22:31
@@ -17,7 +17,6 @@
if c[i, j] > z :
z = c[i, j]
if c[i, j] == z :
-					u = src[i-z+1:i]
src_m = (i-z+1, i+1)
dst_m = (j-z+1, j+1)
else :
```