386. Lexicographical Numbers

Given an integer n, return 1 - n in lexicographical order.

For example, given 13, return: [1,10,11,12,13,2,3,4,5,6,7,8,9].

Please optimize your algorithm to use less time and space. The input size may be as large as 5,000,000.

一刷
题解：
优先级从大到小：

1. *10（保证首部相同）
2. 如果个位数字不为9， ++
3. 如果为9， 则从个，十， 百，知道找到一个不为9， 取该位+1， 移除为9的位。

class Solution {
    public List lexicalOrder(int n) {
         List res = new ArrayList<>(n);
        int curr = 1;
        for(int i=1; i<=n; i++){
            res.add(curr);
            if(curr*10<=n) curr = 10*curr;
            else if(curr%10 != 9 && curr+1<=n) curr++;
            else{
                while((curr/10)%10 == 9){
                    curr /=10;
                }
                curr = curr/10 + 1;
            }
        }
        return res;
    }
}