package books;

/**

* @program JavaBooks

* @description: 1~n整数中1出现的次数

* @author: mf

* @create: 2019/09/26 09:48

*/

/*

输入一个整数n，求1～n这n个整数的十进制表示中1出现的

次数。例如，输入12，1～12这些整数中包含1的数字有1、10

、11和12，1一共出现了5次

*/

public class T43 {

public static void main(String[] args) {

// int count = numberOfBetweenAndN(12);

int count = numberOfBetweenAndN2(12);

System.out.println(count);

}

private static int numberOfBetweenAndN(int num) {

int count = 0;

for (int i = 0; i <= num; i++) {

String n = String.valueOf(i);

for (int j = 0; j < n.length(); j++) {

if ('1' == n.charAt(j)) {

count++;

}

}

}

return count;

}

private static int numberOfBetweenAndN2(int num) {

int count = 0;

for (int i = 1; i <= num; i++) {

int n = i;

while (n != 0) {

if (n % 10 == 1) {

count++;

}

n /= 10;

}

}

return count;

}

}