update 28.找出字符串中第一个匹配项的下标 about

problems/0028.实现strStr.md

@@ -1299,6 +1299,53 @@ impl Solution {
 }
 ```
 
+> 前缀表统一减一
+
+```rust
+impl Solution {
+    pub fn get_next(mut next: Vec<i32>, s: &Vec<char>) -> Vec<i32> {
+        let mut j = -1;
+        for i in 1..s.len() {
+            while j >= 0 && s[(j + 1) as usize] != s[i] {
+                j = next[j as usize];
+            }
+            if s[i] == s[(j + 1) as usize] {
+                j += 1;
+            }
+            next[i] = j;
+        }
+        next
+    }
+    pub fn str_str(haystack: String, needle: String) -> i32 {
+        if needle.is_empty() {
+            return 0;
+        }
+        if haystack.len() < needle.len() {
+            return -1;
+        }
+        let (haystack_chars, needle_chars) = (
+            haystack.chars().collect::<Vec<char>>(),
+            needle.chars().collect::<Vec<char>>(),
+        );
+        let mut j = -1;
+        let mut next = vec![-1; needle.len()];
+        next = Self::get_next(next, &needle_chars);
+        for (i, v) in haystack_chars.into_iter().enumerate() {
+            while j >= 0 && v != needle_chars[(j + 1) as usize] {
+                j = next[j as usize];
+            }
+            if v == needle_chars[(j + 1) as usize] {
+                j += 1;
+            }
+            if j == needle_chars.len() as i32 - 1 {
+                return (i - needle_chars.len() + 1) as i32;
+            }
+        }
+        -1
+    }
+}
+```
+
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