Isaac Tonyloi

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# Implement StrStr

## 28. Implement strStr()

### Easy

Implement strStr().

Given two strings `needle` and `haystack`, return the index of the first occurrence of `needle` in `haystack`, or `-1` if `needle` is not part of `haystack`.

Clarification:

What should we return when `needle` is an empty string? This is a great question to ask during an interview.

For the purpose of this problem, we will return 0 when `needle` is an empty string. This is consistent to C's strstr() and Java's indexOf().

Example 1:

```Input: haystack = "hello", needle = "ll"
Output: 2
```

Example 2:

```Input: haystack = "aaaaa", needle = "bba"
Output: -1
```

Constraints:

• `1 <= haystack.length, needle.length <= 104`
• `haystack` and `needle` consist of only lowercase English characters.

Python solution

``````class Solution:
def strStr(self, haystack: str, needle: str) -> int:

for i in range(len(haystack)):
if haystack[i: i + len(needle)] == needle:
return i
return -1
``````