给定一个正数num，要返回一个大于num的数，并且每一位和相邻位的数字不能相等.
返回达标的数字中，最小的那个。

从左往右看，是否有相邻两位相同的数字。如果有，则低位加1，低位右边全变成0，递归。

代码用rust编写。代码如下：

fn main() {
    let answer = near(766665);
    println!("answer = {}", answer);
}

fn near(num: isize) -> isize {
    // num = 174
    // "0175"
    // num = 899
    // "0900"
    // num = 999
    // "01000"
    let mut raw = format!("0{}", num + 1).chars().collect::<Vec<_>>();
    process(&mut raw);
    return raw.iter().collect::<String>().parse::<isize>().unwrap();
}

fn process(raw: &mut Vec<char>) {
    for i in 1..raw.len() {
        if raw[(i - 1) as usize] == raw[i as usize] {
            add_one(raw, i as isize);
            for j in i + 1..raw.len() {
                raw[j as usize] = '0';
            }
            process(raw);
            return;
        }
    }
}

// 99.....
//  +1
//100
fn add_one(r: &mut Vec<char>, i: isize) {
    let mut i: isize = i;
    while r[i as usize] == '9' {
        r[i as usize] = '0';
        i -= 1;
    }
    r[i as usize] = (r[i as usize] as u8 + 1) as char;
}

执行结果如下：