# [LeetCode] Top Interview 150 Problems Solving # 28 Find the Index of the First Occurrence in a String

# **Understanding the Problem**

There are two strings given as `haystack` and `needle`. `needle` is the string that could be included in `haystack` or not included. If it is included, return the first index that `needle` occurs. If it is not included in `haystack`, return `-1`.

For example, if `haystack = "sadbutsad"` and `needle = "sad"`, the string `”sad”` occurs at the index `0` and `6`, so return `0`.

# **Approach**

My approach is to check whether `needle` is in `haystack`, then find the first index.

# **Solution**

1. Check if `needle` is in `haystack` by `if needle in haystack` clause
    
2. If it exists in `haystack`, then use `find()` method to get the first index of the `needle` and return it
    
3. If it does not exist in `haystack`, return `-1`
    

```python
class Solution:
    def strStr(self, haystack: str, needle: str) -> int:
        return haystack.find(needle) if needle in haystack else -1
```

# **Reflection**

I was wondering if I should use two pointers to solve this problem, but no need for that, as there are internal functions and methods to use.