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#!/usr/bin/env python
# Challenge 099
#
# TASK #2 > Unique Sub-sequence
# Submitted by : Mohammad S Anwar
# You are given two strings $S and $T.
#
# Write a script to find out count of different unique sub-sequences matching
# $T without changing the position of characters.
#
# Example 1:
# Input : $S = "littleit', $T = 'lit'
# Output : 5
#
# 1: [lit] tleit
# 2: [li] t[t] leit
# 3: [li] ttlei[t]
# 4: litt[l] e[it]
# 5: [l] ittle[it]
# Example 2:
# Input : $S = "london', $T = 'lon'
# Output : 3
#
# 1: [lon] don
# 2: [lo] ndo[n]
# 3: [l] ond[on]
import sys
def count_subsequences(s, t):
while True:
if t=="":
return 1
elif s=="":
return 0
elif s[0]==t[0]:
return (count_subsequences(s[1:], t[1:]) +
count_subsequences(s[1:], t))
else:
s=s[1:]
print(count_subsequences(sys.argv[1], sys.argv[2]))
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