# Implement strStr() 🚕

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.

# Solution

I don’t know the space and time complexity because I'm using a library function.

Time Complexity

O(n*m)where n is the length of the needle and m is the length of the haystack.Space Complexity

O(1)

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