28. Implement strStr()

Implement strStr().

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

Example 3:

Input: haystack = "", needle = ""
Output: 0

 

Constraints:

  • 0 <= haystack.length, needle.length <= 5 * 104
  • haystack and needle consist of only lower-case English characters.

Rust Solution

struct Solution;

impl Solution {
    fn str_str(haystack: String, needle: String) -> i32 {
        match haystack.find(&needle) {
            Some(index) => index as i32,
            None => -1,
        }
    }
}

#[test]
fn test() {
    assert_eq!(Solution::str_str("hello".to_string(), "ll".to_string()), 2);
    assert_eq!(
        Solution::str_str("aaaaa".to_string(), "bba".to_string()),
        -1
    );
}

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