Problem Description
Count the number of symmetric numbers between 10 and 1000, and print all symmetric numbers. The so-called symmetric number (also known as the palindrome) means that an integer is the same number when viewed from left to right and from right to left. For example: 12321,6226.
public class Test3_1_1 {
static boolean isSym(int n)
{
int over=n%10;
int q=n;
q/=10;
while (q!=0)
{
over=over*10+q%10;
q/=10;
}
if (n==over)
return true;
return false;
}
public static void main(String[] args) {
// TODO Auto-generated method stub
int count=0;
for (int i=10;i<=1000;i++)
{
if (isSym(i)==true)
{
count++;
System.out.println(i);
}
}
System.out.println("count="+count);
}
}
Optimized
public class Test3_1_2 {
static void doc()
{
int[] a=new int[20];
int count=0;
int k,i,j;
for (int n=10;n<=1000;n++)
{
int temp=n;
k=0;
while (temp!=0)
{
a[k++]=temp%10;
temp /= 10;
}
for (i=0,j=k-1;i<j;i++,j--)
if (a[i]!=a[j])
break;
if (i==k/2)
{
count++;
System.out.println(n);
}
}
System.out.println("count="+count);
}
public static void main(String[] args) {
// TODO Auto-generated method stub
doc();
}
}
After optimization with Java features
public class Test3_1_3 {
static void f()
{
int count=0;
ok:for (int n=10;n<=1000;n++)
{
String s=Integer.toString(n);
for (int i=0;i<s.length();i++)
{
if (s.charAt(i)!=s.charAt(s.length()-1-i))
continue ok;
}
count++;
System.out.println(n);
}
System.out.println("count="+count);
}
public static void main(String[] args) {
// TODO Auto-generated method stub
f();
}
}