Program to count number of distinct substrings in s in Python

Suppose we have a string s, we have to find the number of distinct non-empty substrings of s.

So, if the input is like s = "abaa", then the output will be 8 because, the substrings are ["a", "b", "ab", "ba", "aa", "aba", "baa", "abaa"].

To solve this, we will follow these steps −

• trie := a new map
• n := size of s
• for i in range 0 to n - 1, do
  • curr := trie
  • for j in range i to n - 1, do
    • c := s[j]
    • if c not in curr, then
      • curr[c] := a new map
    • curr := curr[c]
    • curr["*"] := True
• q := make a queue, and insert trie
• ans := 0
• while q is non-empty, do
  • ans := ans + 1
  • t := left item of q, and delete this item from q
  • for each c in t, do
    • if c is not same as "*", then
      • insert t[c] at the end of q
• return ans - 1

Example

Let us see the following implementation to get better understanding −

from collections import deque
def solve(s):
   trie = {}
   n = len(s)
   for i in range(n):
      curr = trie
      for j in range(i, n):
         c = s[j]
         if c not in curr:
            curr[c] = {}
         curr = curr[c]
         curr["*"] = True

   q = deque([trie])
   ans = 0
   while q:
      ans += 1
      t = q.popleft()
      for c in t:
         if c != "*":
            q.append(t[c])
   return ans - 1

s = "abaa"
print(solve(s))

Input

"abaa"

Output

8