# Program to check two strings are 0 or 1 edit distance away or not in Python

PythonServer Side ProgrammingProgramming

Suppose we have two strings S and T we have to check whether they are one or zero edit distance away or not. An edit operation can be defined as deleting a character, adding a character, or replacing a character with another character.

So, if the input is like S = "hello", T = "hallo", then the output will be True, as these two strings have edit distance of 1.

To solve this, we will follow these steps −

• m := size of S, n := size of T
• i := 0, j := 0
• count := 0
• if |m - n| > 1, then
• return False
• while i < m and j < n, do
• if S[i] is not same as T[j], then
• if count is same as 1, then
• return False
• if m < n, then
• j := j + 1
• otherwise when m > n, then
• i := i + 1
• otherwise,
• i := i + 1, j := j + 1
• count := count + 1
• otherwise,
• i := i + 1, j := j + 1
• return True

Let us see the following implementation to get better understanding −

## Example

Live Demo

class Solution:
def solve(self, S, T):
m, n = len(S), len(T)
i, j = 0, 0
count = 0
if abs(m - n) > 1:
return False
while i < m and j < n:
if S[i] != T[j]:
if count == 1:
return False
if m < n:
j += 1
elif m > n:
i += 1
else:
i += 1
j += 1
count += 1
else:
i += 1
j += 1
return True
ob = Solution()
S = "hello"
T = "hallo"
print(ob.solve(S, T))

## Input

"hello", "hallo"

## Output

True