题解 | 整数中1出现的次数（从1到n整数中1出现的次数）

import java.util.*;
public class Solution {
    public int NumberOf1Between1AndN_Solution(int n) {
        int sum = 0;
        for(int i = 1; i<= n;i++){
            sum += countOne(i);
        }
        return sum;
    }

    // 计算一个整数num中有多少个1
    public int countOne(int num){
        int count = 0;
    
        while(num != 0){
            if(num % 10 == 1){
                count++;
            }
            num /= 10;
        }
    

        return count;
    }
}