UVa - 12050

Posted 2020-09-26 Dysania_l

A palindrome is a word, number, or phrase that reads the same forwards as backwards. For example,
the name “anna” is a palindrome. Numbers can also be palindromes (e.g. 151 or 753357). Additionally
numbers can of course be ordered in size. The first few palindrome numbers are: 1, 2, 3, 4, 5, 6, 7, 8,
9, 11, 22, 33, ...
The number 10 is not a palindrome (even though you could write it as 010) but a zero as leading
digit is not allowed.
Input
The input consists of a series of lines with each line containing one integer value i (1 ≤ i ≤ 2 ∗ 109
).
This integer value i indicates the index of the palindrome number that is to be written to the output,
where index 1 stands for the first palindrome number (1), index 2 stands for the second palindrome
number (2) and so on. The input is terminated by a line containing ‘0’.
Output
For each line of input (except the last one) exactly one line of output containing a single (decimal)
integer value is to be produced. For each input value i the i-th palindrome number is to be written to
the output.
Sample Input
1
12
24
0
Sample Output
1
33
151

题意：

输出从1开始第i个回文数字，

思路;

只讲思路不贴代码

先将每个位数的回文数字数量存进去，如1位有9个回文，2位数：9， 三位数 ：90，四位数：90；

然后由于数字是回文的，所以前一半的数字即可，

因为前一半数字的变化依据的仍然是和上一段结尾的距离 如：12的前一段结尾为9 距离为3，要想变化只能第一位往上加，加三次得：33。

具体推一下便知。