int n;
printf("Enter a number : ");
scanf("%d", &n);
if(n < 10)
printf("The number %d has 1 digits", n);
else if(n < 100)
printf("The number %d has 2 digits", n);
else if(n < 1000)
printf("The number %d has 3 digits", n);
else if(n < 10000)
printf("The number %d has 4 digits", n);
原文:https://www.cnblogs.com/cjbsai/p/14634976.html