2022-10-19：一个数组如果满足 : 升降升降升降... 或者 降升降升...都是满足的 给定一个数组， 1，看有几种方法能够剔除一个元素，达成上述的要求

use rand::Rng;
use std::iter::repeat;
fn main() {
    let max_len: i32 = 10;
    let max_value: i32 = 100;
    let test_time: i32 = 30000;
    println!("测试开始");
    for _ in 0..test_time {
        let len: i32 = rand::thread_rng().gen_range(0, max_len) + 1;
        let mut arr = random_array(len, max_value);
        let ans1 = ways1(&mut arr);
        let ans2 = ways2(&mut arr);
        if ans1 != ans2 {
            println!("出错了!");
            for num in &arr {
                print!("{} ", num);
            }
            println!("");
            println!("ans1 = {}", ans1);
            println!("ans2 = {}", ans2);
            break;
        }
    }
    println!("测试结束");
}

// 暴力方法
// 为了验证
fn ways1(arr: &mut Vec<i32>) -> i32 {
    if is_wiggle(arr, -1) {
        return 0;
    }
    let mut ans = 0;
    for i in 0..arr.len() as i32 {
        if is_wiggle(arr, i) {
            ans += 1;
        }
    }
    return if ans == 0 { -1 } else { ans };
}

fn is_wiggle(arr: &mut Vec<i32>, remove_index: i32) -> bool {
    let mut ans = true;
    // 升
    let mut request = true;
    for i in 1..arr.len() as i32 {
        if i == remove_index {
            continue;
        }
        if i - 1 == remove_index && remove_index == 0 {
            continue;
        }
        let last = if i - 1 == remove_index { i - 2 } else { i - 1 };
        if request {
            if arr[last as usize] >= arr[i as usize] {
                ans = false;
                break;
            }
        } else {
            if arr[last as usize] <= arr[i as usize] {
                ans = false;
                break;
            }
        }
        request = !request;
    }
    if ans {
        return true;
    }
    ans = true;
    // 降
    request = false;
    for i in 1..arr.len() as i32 {
        if i == remove_index {
            continue;
        }
        if i - 1 == remove_index && remove_index == 0 {
            continue;
        }
        let last = if i - 1 == remove_index { i - 2 } else { i - 1 };
        if request {
            if arr[last as usize] >= arr[i as usize] {
                ans = false;
                break;
            }
        } else {
            if arr[last as usize] <= arr[i as usize] {
                ans = false;
                break;
            }
        }
        request = !request;
    }
    return ans;
}

// 时间复杂度O(N)
fn ways2(arr: &mut Vec<i32>) -> i32 {
    if arr.len() < 2 {
        return 0;
    }
    let n = arr.len() as i32;
    let mut right_up: Vec<bool> = repeat(false).take(n as usize).collect();
    let mut right_down: Vec<bool> = repeat(false).take(n as usize).collect();
    right_up[(n - 1) as usize] = true;
    right_down[(n - 1) as usize] = true;
    let mut i = n - 2;
    while i >= 0 {
        right_up[i as usize] =
            arr[i as usize] < arr[(i + 1) as usize] && right_down[(i + 1) as usize];
        right_down[i as usize] =
            arr[i as usize] > arr[(i + 1) as usize] && right_up[(i + 1) as usize];
        i -= 1;
    }
    // 数组是不是天然符合！
    if right_up[0] || right_down[0] {
        return 0;
    }
    // 删掉0位置的数，数组达标还是不达标！
    // 1 升
    // 1 降
    let mut ans = if right_up[1] || right_down[1] { 1 } else { 0 };
    // ...[0]
    let mut left_up = true;
    let mut left_down = true;
    let mut tmp;
    let mut i = 1;
    let mut l = 0;
    let mut r = 2;
    while i < n - 1 {
        ans += if arr[l] > arr[r] && right_up[r] && left_down
            || arr[l] < arr[r] && right_down[r] && left_up
        {
            1
        } else {
            0
        };
        // i（两个信息） i+1
        // 变量复用
        //			boolean curLeftUp = arr[l] > arr[i] && leftDown;
        //			boolean curLeftDown =  arr[l] < arr[i] && leftUp;
        //			leftUp = curLeftUp;
        //			leftDown = curLeftDown;
        tmp = left_up;
        // 7 4
        left_up = arr[l] > arr[i as usize] && left_down;
        left_down = arr[l] < arr[i as usize] && tmp;
        i += 1;
        l += 1;
        r += 1;
    }
    // 单独算一下 删掉n-1位置数的时候
    ans += if left_up || left_down { 1 } else { 0 };
    return if ans == 0 { -1 } else { ans };
}

// 为了测试
fn random_array(len: i32, max_value: i32) -> Vec<i32> {
    let mut arr: Vec<i32> = vec![];
    for _i in 0..len {
        arr.push(rand::thread_rng().gen_range(0, max_value) + 1);
    }
    return arr;
}