Daily practice Blue Bridge Cup C/C++ Group B ~ House Number Production
topic:
Xiaolan wants to make house numbers for the residents of a street.
This street has a total of 2020 residents, with house numbers from 1 to 2020.
The method of Xiaolan to make the house number is to first make the number characters from 0 to 9, and finally paste the characters on the house number as needed. For example, the house number 1017 needs to paste the characters 1, 0, 1, and 7 in sequence, that is, one character 0 is required. 2 characters 1, 1 character 7.
How many characters 2 are needed in total to make all the number 1 to 2020?
Ideas : I wrote the ideas in the code comments. This is a fill-in-the-blank question, and you can directly output the answer after calculating it.
#include <stdio.h>
#include <stdlib.h>
/**
*小蓝要为一条街的住户制作门牌号。
*这条街一共有 20202020 位住户，门牌号从 11 到 20202020 编号。
*小蓝制作门牌的方法是先制作 00 到 99 这几个数字字符，最后根据需要将字符粘贴到门牌上，
*例如门牌 1017 需要依次粘贴字符 1、0、1、71、0、1、7，即需要 11 个字符 00，22 个字符 11，11 个字符 77。
*请问要制作所有的 11 到 20202020 号门牌，总共需要多少个字符 22？
*/
int main() {
int num=0;//定义2的数量
int j,i;
for( i=1;i<= 2020;i++)
{
j=i;
while(j){
if(j%10==2){
//如果2%10等于2，num加1
num++;
}
j /=10; //20/10等于2，然后2等于j，代入循环，2%10等于2，又num加1。
}
}
printf("%d",num);
return 0;
}
Answer:624