Program to find number of subsequence that are present inside word list in python

Suppose we have a list of words and a string s, we have to find the number of strings in the words list that are subsequences of s.

So, if the input is like words = ["xz", "xw", "y"] s = "xyz", then the output will be 2, as "xz" and "y" are subsequences of "xyz".

To solve this, we will follow these steps −

  • ans := 0
  • d := an empty map
  • for each word in words, do
    • insert word at the end of d[word[0]]
  • for each c in s, do
    • l := d[c]
    • d[c] := a new list
    • for each word in l, do
      • if size of word is 1, then
        • ans := ans + 1
      • otherwise,
        • insert substring of word[from index 1 to end] at the end of d[word[1]]
  • return ans

Let us see the following implementation to get better understanding −


Live Demo

from collections import defaultdict
class Solution:
   def solve(self, words, s):
      ans = 0

      d = defaultdict(list)
      for word in words:

      for c in s:
         l = d[c]
         d[c] = []

         for word in l:
            if len(word) == 1:
               ans += 1
      return ans
ob = Solution()
words = ["xz", "xw", "y"]
s = "xyz"
print(ob.solve(words, s))


["xz", "xw", "y"], "xyz"



Updated on: 02-Dec-2020


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