> For the complete documentation index, see [llms.txt](https://r24zeng.gitbook.io/leetcode-notebook/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://r24zeng.gitbook.io/leetcode-notebook/bu-chong-4060-dao/158.-read-n-characters-given-read4-ii-call-multiple-times.md).

# 160. One Edit Distance

{% hint style="success" %}
题意：两个字符串`s`和`t`，要让s执行一次变换变成t

返回**True**，否则**False**，只有三种形式的变换：

1. insert one char into `s` to get `t`, **eg. "ab" -> "acb"**
2. delete one char from `s` to get `t`, **eg. "abc" -> "ab"**
3. replace one char of `s` to get `t`, **eg. "1203" -> "1213"**
   {% endhint %}

### Solutions:

1. if length difference is bigger than 1, return False
2. if length difference is equal to 1, then only allow one char different, longer string moves to next char
3. if length difference is 0, then only allow one char different, both strings move to next char

```python
class solution:
    def isOneEditDistance(s: string, t: string):
        n = len(s)
        m = len(t)
        if abs(n-m) > 1:
            return False
        if n - m == 1:
            for i in range(n):
                if s[i] != t[i]:
                    return s[i+1:] == t[i:]:
        elif m - n == 1:
            for i in range(m):
                if s[i] != t[i]:
                    return s[i:] != t[i+1:]:
        elif m == n:
            for i in range(n):
                if s[i] != t[i]:
                    return s[i+1:] != t[i+1:]:
```