LeetCode每日一题(28. Find the Index of the First Occurrence in a String)

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.

Example 1:

Input: haystack = “sadbutsad”, needle = “sad”
Output: 0

Explanation: “sad” occurs at index 0 and 6.
The first occurrence is at index 0, so we return 0.

Example 2:

Input: haystack = “leetcode”, needle = “leeto”
Output: -1

Explanation: “leeto” did not occur in “leetcode”, so we return -1.

Constraints:

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

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用 Rabin-Karp 算法

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impl Solution {
   
   
    pub fn str_str(haystack: String, needle: String) -> i32 {
   
   
        let needle_hash = needle.chars().