在1到100中有9的数有9,19,29,39,49,59,69,79,89,90,91,92,93,94,95,96,97,98,99
不难看出分两种情况1是除以10取模/取余等于9
int main()
{
int i = 0;
int count = 0;
for (i = 1; i <= 100; i++)
{
if (i % 10 == 9)
count++;
else if (i / 10 == 9)//把else去掉要是不去掉就会少一个,将其看成两个分支
count++;
}
printf("count=%d\n", count);
return 0;
}