substring.py

#/usr/bin/python

import sys

# quadratic time (inefficient) common substring algorithm



def lcs(s1,s2):
    max=0
    ans={}
    ret=[]
    for i in range(len(s1)):
        ans[i]={}
        for j in range(len(s2)):
            if s1[i]==s2[j]:
                if i==0 or j==0:
                    ans[i][j]=1
                else:
                    ans[i][j]=ans[i-1][j-1]+1
                if ans[i][j]>max:
                    max=ans[i][j]
                    ret=[[i-max+1,j-max+1,max]]
                elif ans[i][j]==max:
                    ret.append([i-max+1,j-max+1,max])
            else:
                ans[i][j]=0
    return(ret)

                


try:
    f=open(sys.argv[1],'rU')
except:
    f=sys.stdin

value,key,s="","",{}

for x in f:
    if x[0]!=">":
        value=value+x.strip()
    else:
        if key!="": s[key]=value
        value=''
        key=x[1:].strip()
s[key]=value


first_key,first_value=s.popitem()
for x in s:
    a=lcs(first_value,s[x])
    first_value=a

print first_value