Rust每日一练(Leetday0020) 最后单词的长度、螺旋矩阵II、排列序列

fn length_of_last_word(s: String) -> i32 {
    let strs: Vec<&str> = s.trim().split(' ').collect();
    for i in (0..strs.len()).rev() {
        if !strs[i].is_empty() {
            return strs[i].len() as i32;
        }
    }
    return 0;
}
fn main() {
    let s = "Hello World".to_string();
    println!("{:?}", length_of_last_word(s));
    let s = "   fly me   to   the moon  ".to_string();
    println!("{:?}", length_of_last_word(s));
    let s = "luffy is still joyboy".to_string();
    println!("{:?}", length_of_last_word(s));
}

fn length_of_last_word(s: String) -> i32 {
    let bytes = s.into_bytes();
    let n = bytes.len();
    let mut i = n as isize - 1;
    while i >= 0 && bytes[i as usize] == b' ' {
        i -= 1;
    }
    if i < 0 {
        return 0;
    }
    let mut j = i;
    while j >= 0 && bytes[j as usize] != b' ' {
        j -= 1;
    }
    return (i - j) as i32;
}
fn main() {
    let s = "Hello World".to_string();
    println!("{:?}", length_of_last_word(s));
    let s = "   fly me   to   the moon  ".to_string();
    println!("{:?}", length_of_last_word(s));
    let s = "luffy is still joyboy".to_string();
    println!("{:?}", length_of_last_word(s));
}

fn generate_matrix(n: i32) -> Vec<Vec<i32>> {
    let mut matrix = vec![vec![0; n as usize]; n as usize];
    let (mut num, mut left, mut right, mut top, mut bottom) = (1, 0, n - 1, 0, n - 1);
    while left <= right && top <= bottom {
        for i in left..=right {
            matrix[top as usize][i as usize] = num;
            num += 1;
        }
        for i in top + 1..=bottom {
            matrix[i as usize][right as usize] = num;
            num += 1;
        }
        if left < right && top < bottom {
            for i in (left..right).rev() {
                matrix[bottom as usize][i as usize] = num;
                num += 1;
            }
            for i in (top + 1..bottom).rev() {
                matrix[i as usize][left as usize] = num;
                num += 1;
            }
        }
        left += 1;
        right -= 1;
        top += 1;
        bottom -= 1;
    }
    matrix
}
fn main() {
    let n = 3;
    println!("{:?}", generate_matrix(n));
    println!("{:?}", generate_matrix(1));
}

fn generate_matrix(n: i32) -> Vec<Vec<i32>> {
    let mut matrix = vec![vec![0; n as usize]; n as usize];
    let mut num = 1;
    let mut row = 0;
    let mut col = 0;
    let mut direction = 0;
    let directions = vec![vec![0, 1], vec![1, 0], vec![0, -1], vec![-1, 0]];
    while num <= n * n {
        matrix[row as usize][col as usize] = num;
        num += 1;
        let next_row = row + directions[direction][0];
        let next_col = col + directions[direction][1];
        if next_row < 0 || next_row >= n || next_col < 0 || next_col >= n || matrix[next_row as usize][next_col as usize] != 0 {
            direction = (direction + 1) % 4;
        }
        row += directions[direction][0];
        col += directions[direction][1];
    }
    matrix
}
fn main() {
    let n = 3;
    println!("{:?}", generate_matrix(n));
    println!("{:?}", generate_matrix(1));
}

use std::convert::TryInto;
fn factorial(n: usize) -> usize {
    (1..=n).product()
}
fn get_permutation(n: i32, k: i32) -> String {
    let mut nums: Vec<i32> = (1..=n).collect();
    let mut res = String::new();
    nums.sort();
    let mut k = k - 1;
    for i in (1..=n).rev() {
        let f = factorial((i-1).try_into().unwrap()) as i32;
        let index = (k / f) as usize;
        res.push_str(&nums[index].to_string());
        nums.remove(index);
        k %= f;
    }
    res
}
fn main() {
    let n = 3;
    let k = 3;
    let s = get_permutation(n, k);
    println!("{}", s);
    let n = 4;
    let k = 9;
    let s = get_permutation(n, k);
    println!("{}", s);
    let n = 3;
    let k = 1;
    let s = get_permutation(n, k);
    println!("{}", s);
}