Find The Index Of The First Occurrence In A String · Interview Problem

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Leetcode

Easy

Strings

Arrays

Google

Find The Index Of The First Occurrence In A String

Find the first position where one string appears as a substring inside another string.

Acceptance 85%

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Implement strStr()

gfg

Primary

Problem Statement

Given two strings, haystack and needle, return the index of the first occurrence of needle in haystack. If needle does not appear in haystack, return -1.

The match must be contiguous and exact. If needle is empty, the answer is 0 by convention.

Input Format

A string haystack
A string needle

Output Format

Return a single integer: the first index where needle starts in haystack, or -1 if it does not occur

Constraints

0 <= |haystack|, |needle| <= $10^{4}$
Strings contain arbitrary lowercase or ASCII characters depending on platform variant
The answer fits in a 32-bit signed integer

Examples

Sample cases returned by the problem API.

Example 1

Input

haystack = "sadbutsad", needle = "sad"

Output

Explanation

The substring "sad" appears at index 0 and again later, but we return the first occurrence.

Example 2

Input

haystack = "leetcode", needle = "leeto"

Output

-1

Explanation

The string "leeto" does not occur as a contiguous substring of "leetcode".

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