2023-01-08：小红定义一个仅有r、e、d三种字符的字符串中，如果仅有一个长度不小于2的回文子串，那么这个字符串定义为"好

use std::iter::repeat;
fn main() {
    for i in 1..=10 {
        println!("长度为{}, 答案:{},{}", i, num1(i), num2(i));
    }
}

// 暴力方法
// 为了观察规律
// 具体方法论，在体系学习班，章节39 : 根据对数器找规律
fn num1(n: i32) -> i32 {
    let mut p: Vec<u8> = repeat(0).take(n as usize).collect();
    return process1(&mut p, 0);
}

fn process1(p: &mut Vec<u8>, i: i32) -> i32 {
    if i == p.len() as i32 {
        let mut dp = get_manacher_dp(p);
        let mut cnt = 0;
        for p in dp.iter() {
            if p - 1 > 3 {
                return 0;
            }
            if p - 1 >= 2 {
                cnt += 1;
            }
            if cnt > 1 {
                return 0;
            }
        }
        return if cnt == 1 { 1 } else { 0 };
    } else {
        let mut ans = 0;
        p[i as usize] = 'r' as u8;
        ans += process1(p, i + 1);
        p[i as usize] = 'e' as u8;
        ans += process1(p, i + 1);
        p[i as usize] = 'd' as u8;
        ans += process1(p, i + 1);
        return ans;
    }
}

fn get_manacher_dp(s: &mut Vec<u8>) -> Vec<i32> {
    let mut str = manacher_string(s);
    let mut p_arr: Vec<i32> = repeat(0).take(str.len()).collect();
    let mut cc = -1;
    let mut rr = -1;
    for i in 0..str.len() as i32 {
        p_arr[i as usize] = if rr > i {
            get_min(p_arr[(2 * cc - i) as usize], rr - i)
        } else {
            1
        };
        while i + p_arr[i as usize] < str.len() as i32 && i - p_arr[i as usize] > -1 {
            if str[(i + p_arr[i as usize]) as usize] == str[(i - p_arr[i as usize]) as usize] {
                p_arr[i as usize] += 1;
            } else {
                break;
            }
        }
        if i + p_arr[i as usize] > rr {
            rr = i + p_arr[i as usize];
            cc = i;
        }
    }
    return p_arr;
}

fn get_min<T: Clone + Copy + std::cmp::PartialOrd>(a: T, b: T) -> T {
    if a < b {
        a
    } else {
        b
    }
}

fn manacher_string(s: &mut Vec<u8>) -> Vec<u8> {
    let mut res: Vec<u8> = repeat(0).take(s.len() * 2 + 1).collect();
    let mut index = 0;
    let mut i = 0;
    while i != res.len() {
        res[i as usize] = if (i & 1) == 0 {
            '#' as u8
        } else {
            index += 1;
            s[index - 1]
        };
        i += 1;
    }
    return res;
}

// 正式方法
// 观察规律之后，把规律变成代码
fn num2(n: i32) -> i32 {
    if n == 1 {
        return 0;
    }
    if n == 2 {
        return 3;
    }
    if n == 3 {
        return 18;
    }
    return 6 * (n + 1);
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.17;

contract Hello{
    function main() public pure returns (int32[] memory){
        int32[] memory ans = new int32[](10);
    for (int32 i = 1; i <= 10; i++) {
      ans[uint32(i-1)] = num2(i);
    }
    return ans;
    }

  // 正式方法
  // 观察规律之后，把规律变成代码
  function  num2(int32 n) public pure returns(int32) {
    if (n == 1) {
      return 0;
    }
    if (n == 2) {
      return 3;
    }
    if (n == 3) {
      return 18;
    }
    return 6 * (n + 1);
  }

}