两个代码换了相等的参数的位置，一个正确一个错误

Question

#include
using namespace std;
void main()
{
for (int n = 100; n < 1000; ++n) {
int num=n;
int sum = 0;
while (n) {
sum += n% 10;
n/= 10;
}
if (sum == 5)
cout << num << " ";
}
}

正确
#include
using namespace std;
void main()
{
for (int n = 100; n < 1000; ++n) {
int num=n;
int sum = 0;
while (num) {
sum += num% 10;
num/= 10;
}
if (sum == 5)
cout << n<< " ";
}
}
题目是输出100到1000中各位数和为5的数，为啥while循环用num就正确，用n就不对