Chang'an(Palindrome Numbers-回文数字统计)

统计前半个回文串

#include <bits/stdc++.h>using namespace std;#define For(i,n) for(int i=1;i<=n;i++)#define ForD(i,n) for(int i=n;i;i--)#define ForkD(i,k,n) for(int i=n;i>=k;i--)#define Rep(i,n) for(int i=0;i<n ;i++)#define MAXN (1000000000+10)int n;int s[100000];int main(){//freopen("J.in","r",stdin);while(scanf("%d",&n)!=EOF&&n){int t=1; //位数int p=9;while (n>p){t++;n-=p;if (t>=3&&t%2==1){p*=10;}} int len=t/2+t%2;//cout<<p<<endl;/*int a=(n-1)/(p/9)+1;*/int k10=p/9;n+=k10-1;ForD(i,len){s[i]=n%10;n/=10;}For(i,len) printf("%d",s[i]);if (t%2) len--;ForD(i,len) printf("%d",s[i]);//cout<<n<<endl;printf("\n");}return 0;}