Question

Problem 1

Substring matching is the process of determining whether shorter string (the substring) is contained within a longer string. Substring matching plays important roles in the reconstruction of an unknown DNA string from pieces, and in searching for interesting substrings within a known DNA string.

Python provides a find (substring, start, end) string method that returns the lowest index (integer) where the substring is found in the index range start <= index < end. The start and end arguments are optional, but for this exercise we will make them required (you will learn later how to handle optional arguments). If the substring is not found, -1 is returned.

Without using the find string method, write a function name multi_find(some_string, sub_string, start, end) that, instead of returning one integer index, returns a string that contains zero or more indices separated by commas. In this case, the string will contain digits representing the integer indices. If the substring is not found, an empty string is returned.

output:

Please enter a string: this is a test string that tests are done on it successfully.

Please enter a substring: test

Please enter search starting index: 0

please enter search end index: 1000

found substrings: 10,27

would you like to continue (yes/no)? yes

This is a python problem. please help me to make this program.

Answer 1

#code screenshot

#code

def multi_find(string, sub, start, end): #multi_find function implementation
found = "" #found string stores the indices
i = start
while(i<=end and i<len(string)): #loops through the str until i reaches end or string length
k = i  
for c in sub: #loops through sub substring and
if c == string[k]: #checks if the c matches with string[k]
k += 1 #if it matches then increments k value by 1
else: #else breaks the loop
break

if(k-i==len(sub)): #if k-i is equal to length of sub string
if(len(found)>0): #if length of found is greater than 0 then
found += "," #appends , to the found string
found += str(i) #append the index to found
i = i+k #increments i value by k
else:
i = i+1 #else adds i value by 1
return found

while(True): #loops unitl user enters no
#prompts the user for the values
s = input("Please enter a string: ")
sub = input("Please enter a substring: ")
start = int(input("Please enter search starting index: "))
end = int(input("Please enter search end index: "))
print("found substrings: ",multi_find(s, sub, start, end)) #calls the multi_find function
choose = input("would you like to continue(yes/no)?")
if(choose=="no"):
break
  
  

#output screenshot

#any query, post in the comment section