Problem Statement

Given two strings str1 and str2, return the index of first occurrences of the str2 string in str1. If str2 doesn't exists in str1 string, return -1.

Examples

• Example 1:

  • Input: str1 = "algorithms", str2 = "rith"
  • Expected Output: 4
  • Justification: The substring "rith" begins at index 4 in the string "algorithms".

• Example 2:

  • Input: str1 = "openai", str2 = "ai"
  • Expected Output: 4
  • Justification: The substring "ai" starts at index 4 in the string "openai".

• Example 3:

  • Input: str1 = "challenge", str2 = "test"
  • Expected Output: -1
  • Justification: The substring "test" does not appear in the string "challenge", hence the output is -1.

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