Python – Possible Substring count from String

Given target string and argument substring, count how many substrings can be constructed using string characters, repetitions not allowed.

Input : test_str = “geksefokesgergeeks”, arg_str = “geeks” 
Output : 3 
Explanation : “geeks” can be created 3 times using string characters.

Input : test_str = “gefroksefokesgergeeks”, arg_str = “for” 
Output : 2 
Explanation : “for” can be created 2 times using string characters. 

Method #1 : Using count() + min() + set()

The combination of above functions can be used to solve this problem. In this, we divide the count of each element of arg string with count of target string character, and using min(), the lowest element is returned. The logic behind is that any element above min would mean the minimum element would miss from that string onwards.

Python3

# Python3 code to demonstrate working of
# Possible Substring count from String
# Using min() + list comprehension + count()

# initializing string
test_str = "gekseforgeeks"

# printing original string
print("The original string is : " + str(test_str))

# initializing arg string
arg_str = "geeks"

# using min and count to get minimum possible
# occurrence of character
res = min(test_str.count(char) // arg_str.count(char) for char in set(arg_str))

# printing result
print("Possible substrings count : " + str(res))

Output

The original string is : gekseforgeeks
Possible substrings count : 2

Time Complexity: O(n)
Auxiliary Space: O(1)

Method #2 : Using Counter() + list comprehension

This is yet another way in which this task can be performed. In this, we perform the task of counting using Counter() and list comprehension is used to bind the result together, using min() performing similar task as previous method.

Python3

# Python3 code to demonstrate working of
# Possible Substring count from String
# Using Counter() + list comprehension
from collections import Counter

# initializing string
test_str = "gekseforgeeks"

# printing original string
print("The original string is : " + str(test_str))

# initializing arg string
arg_str = "geeks"

# using Counter to get character frequencies
temp1 = Counter(test_str)
temp2 = Counter(arg_str)
res = min(temp1[char] // temp2[char] for char in temp2.keys())

# printing result
print("Possible substrings count : " + str(res))

Output

The original string is : gekseforgeeks
Possible substrings count : 2

The Time and Space Complexity for all the methods are the same:

Time Complexity: O(n)
Auxiliary Space: O(n)

Method 3:  using operator.countOf() method

Python3

# Python3 code to demonstrate working of
# Possible Substring count from String
import operator as op

# initializing string
test_str = "gekseforgeeks"

# printing original string
print("The original string is : " + str(test_str))

# initializing arg string
arg_str = "geeks"

# using min and count to get minimum possible
# occurrence of character
res = min(op.countOf(test_str, char) // op.countOf(arg_str, char)
          for char in set(arg_str))

# printing result
print("Possible substrings count : " + str(res))

Output

The original string is : gekseforgeeks
Possible substrings count : 2

Time Complexity: O(N)
Auxiliary Space : O(1)

Method #4: Using for loop, max_count

Approach:

1. Initialize the test_str and arg_str, max count to cnt variable.
2. Iterate through the each character in arg_str
   1. find the count of the character
   2. compare it with the max count, if it less than the max count
   3. then assign it to cnt.
3. Finally print the count to see the possible substring count.

Python3

# Python3 code to demonstrate working of
# Possible Substring count from String
# Using for loop
# Initializing string
test_str = "geksefokesgergeeks"

# printing original string
print("The original string is: ",test_str)

# Initializing arg string
arg_str = "geeks"

# for unique characters in string
arg_str=set(arg_str)

# Initializing max count
cnt=10000

# using for loop to find the count of each character in
# arg string and at end combination value will be in cnt
for i in arg_str:
    m_cnt=test_str.count(i)
    if m_cnt<cnt:
        cnt=m_cnt
# printing result
print("Possible substrings count: ",cnt)
#This code developed by mohan balaji battu

Output

The original string is:  geksefokesgergeeks
Possible substrings count:  3

Time Complexity: O(N)
Auxiliary Space : O(1)