Check if a string can be repeated to make another string in Python

Suppose we have two strings s and t, we have to find how many times the string s can be concatenated to generate t. If we cannot generate t using s, then return -1.

So, if the input is like s = "tom" t = "tomtomtom", then the output will be 3 as we can concatenate "tom" 3 times to get "tomtomtom".

To solve this, we will follow these steps −

• if size of t is not divisible by size of s, then
  • return -1
• cnt := quotient of (size of t / size of s)
• s := concatenate s cnt number of times
• if s is same as t, then
  • return cnt
• return -1

Let us see the following implementation to get better understanding −

Example

 Live Demo

def solve(s, t):
   if(len(t) % len(s) != 0):
      return -1;
   cnt = int(len(t) / len(s))
   s = s * cnt
   if(s == t):
      return cnt
   return -1
s = "tom"
t = "tomtomtom"
print(solve(s, t))

Input

"tom", "tomtomtom"

Output

3

Arnab Chakraborty

Updated on: 29-Dec-2020

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