50分

zcs2012 @ 2023-12-17 08:43:44

#include<cstdio>
#include<cctype>
#include<cstdlib>
#include<cstring>
int main(){
    char m[70];
    int n;
    scanf("%d%s",&n,m);
    for(int i=0;i<=30;i++){
        char x[70];
        for(int p=strlen(m),k=p;p--;)
            x[p]=m[k-p-1];
        if(!strcmp(m,x))
            printf("STEP=%d\n",i),exit(0);
        char y[70]={};
        int p1=strlen(m);
        memset(y,48,p1+1);
        for(;p1--;){
            int a=isdigit(m[p1])?m[p1]-48:m[p1]-55,b=isdigit(x[p1])?x[p1]-48:x[p1]-55;
//          printf("%d %d ",a,b);
            if((y[p1+1]+=(a+b)%n)>57)y[p1+1]+=7;
//          printf("%d\n",y[p1+1]);
            if(a+b>=n)y[p1]++;
        }
        strcpy(m,y[0]==48?y+1:y);
//      puts(m);
//      putchar('\n');
    }
    puts("Impossible!");
    return 0;
}

by luoguandy @ 2023-12-17 08:59:39

#include<bits/stdc++.h>
using namespace std;
int n1[205],n2[205],step,base;
char c[105];
void add(){
    for(int i=1;i<=200;i++){
        n1[i]+=n2[i];
    }
    for(int i=1;i<=199;i++){
        n1[i+1]+=n1[i]/base;
        n1[i]%=base;
    }
}
int len(int x[]){
    int t;
    for(int i=200;x[i]==0;i--)t=i;
    return t-1;
}
void wrap(){
    int len1=len(n1);
    for(int i=len1;i>=1;i--){
        n2[i]=n1[len1-i+1];
    }
}
bool check(int x[]){
    for(int i=1;i<=len(x)/2+1;i++){
        if(x[i]!=x[len(x)-i+1])return 0;
    }
    return 1;
}
int main(){
    cin>>base>>c;
    for(int i=1;i<=strlen(c);i++){
        if(c[strlen(c)-i]<='9')n1[i]=c[strlen(c)-i]-'0';
        else if(c[strlen(c)-i]>='A'&&c[strlen(c)-i]<='Z')n1[i]=c[strlen(c)-i]-'A'+10;
        else n1[i]=c[strlen(c)-i]-'a'+10;
    }
    for(;step<=30;step++){
        wrap();
        add();
        if(check(n1)){cout<<"STEP="<<step+1;return 0;}
    }
    cout<<"Impossible!";
    return 0;
}