用 Rust 刷 leetcode 第五題

Given a string s, find the longest palindromic substring in s. You may assume that the maximum length of s is 1000.

Example 1:
Input: "babad"
Output: "bab"
Note: "aba" is also a valid answer.

Example 2:
Input: "cbbd"
Output: "bb"

use std::cmp;

impl Solution {
    pub fn longest_palindrome(s: String) -> String {
        let seq: Vec<char> = s.chars().collect();
        let mut len = seq.len();
        if len <= 1 {
            return s;
        }

        //ready for 
        let mut s_new: [char; 2004] = ['\0'; 2004];
        let mut p: [usize; 2004] = [0; 2004];
        s_new[0] = '$';
        s_new[1] = '#';
        let mut j = 2;

        for i in 0..len {
            s_new[j] = seq[i];
            j += 1;

            s_new[j] = '#';
            j += 1;
        }
        s_new[j] = '\0';
        len = j;

        //start
        let mut index: usize = 0;
        let mut max_len:usize = 0;

        let mut center: usize = 0;
        let mut max_right: usize = 0;

        for i in 1..len {
            if i < max_right {
                p[i] = cmp::min(p[2*center-i], max_right-i);
            } else {
                p[i] = 1;
            }

            while s_new[i-p[i]] == s_new[i+p[i]] {
                p[i] += 1;
            }

            if max_right < (p[i] + i) {
                center = i;
                max_right = p[i] + i;
            }

            if (max_len < p[i])
            {
                max_len = p[i] -1;
                index = (2*i-max_right)/2 ;
            }
        }

        let end: usize = index + max_len;
        s[index..end].to_owned()
    }
}

解決方法採用的Manacher演算法，演算法的原理可以參考連結的文章
https://bestsort.cn/2019/04/28/424/

本作品採用《CC 協議》，轉載必須註明作者和本文連結