1到n中1的出现次数

https://blog.csdn.net/yi_Afly/article/details/52012593?depth_1-utm_source=distribute.pc_relevant.none-task-blog-BlogCommendFromBaidu-1&utm_source=distribute.pc_relevant.none-task-blog-BlogCommendFromBaidu-1 这篇博客讲的很清楚，然后要注意10的13次超出了int的表示范围

import java.util.Scanner;

/*
 *
 * https://www.nowcoder.com/practice/38af9b5a06ea4448ae9b2a488b6a991f?tpId=101&&tqId=33140&rp=1&ru=/activity/oj&qru=/ta/programmer-code-interview-guide/question-ranking
 *
 * */
public class Main {
    public static long count(long n) {
        if (n < 1) {
            return 0;
        }
        long count = 0;
        long round = n;
        long weight = 0;
        long base = 1;
        while (round > 0) {
            weight = round % 10;
            round = round / 10;
            count += round * base;
            if (weight == 1) {
                count += n % base + 1;
            } else if (weight > 1) {
                count += base;
            }
            base *=10;
        }
        return count;
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long n = sc.nextLong();
        System.out.println(count(n));
    }
}