```cpp
#include <bits/stdc++.h>
using namespace std;
#define ll long long
int N, M[131], W[131], S[131], len;
int num;
string s1;
inline void init(){
//s1->m
for (int i=0; i<len; ++i){
num = s1[len-1-i]-'0';
num = num >= 10 ? num + '0' - 'A' + 10: num;//注意已经减过
M[i] = num;
}
}
inline bool reverseAndAdd(int *m, int *w, int *s){
//reverse(m)->w
for(int i=0; i<len; ++i){
w[i]=m[len-1-i];
}
//m+w->s
bool c=false;
for(int i=0; i<len; ++i){
s[i]=m[i]+w[i]+c;
c=false;
if(s[i] >= N){
s[i] %= N;
c=true;
}
}
if(c){
s[len]=1;
++len;
}
//check
for(int i=0; i<=len/2+1; ++i){
if(!(s[i]==s[len-1-i])) return false;
}
return true;
}
int main(){
scanf("%lld", &N);
cin>>s1;
len=s1.length();
init();
int *m=M;
int *w=W;
int *s=S;
bool kkk;
kkk=1;
for(int i=0; i<len/2+1; ++i){
if(!(m[i]==m[len-1-i])){
kkk=0;
break;
}
}
if(kkk){//循环自己注意点，逻辑严谨一些
cout<<"STEP=0";
return 0;
}
for(int j=1;j<=30;++j){
if(reverseAndAdd(m,w,s)){
cout<<"STEP="<<j;
return 0;
}
//s->m,m->s
int* temp = s;
s = m;
m = temp;
}
cout<<"Impossible!";
return 0;
}
```
建议自己下载数据调试
by sbno333 @ 2024-01-20 23:13:20