bzoj 3916 暴力哈希

暴力的哈希，注意：

将一个串当作另一个串的前缀，需要乘上p[len],len=后面串的长度

这是自己的代码，拿数据在本地测A掉了，但是bz上wa了？？bz换数据了难道？？

#include<cstdio>
#include<cstring>
#define rep(i,x,y) for(register int i=x;i<=y;i++)
using namespace std;
const int N=2005000;
typedef unsigned long long ull;

int n,mid;
char a[N],ans[N];
ull p[N],sum[N],b;

inline ull get(int l,int r){
    return sum[r]-sum[l-1]*p[r-l+1];}
bool judge(int i){
    ull x,y,la;
    if(i<mid+1){
        x=get(1,i-1)*p[mid+1-i]+get(i+1,mid+1);
        y=get(mid+2,n);
    }else if(i==mid+1){
        x=get(1,mid);
        y=get(mid+2,n);
    }else if(i>mid+1){
        x=get(1,mid);
        y=get(mid+1,i-1)*p[n-i]+get(i+1,n);
    }if(x==y){
        if(x==la) return 0;
        la=x;
        int top=0;
        if(i<=mid+1) rep(j,mid+2,n) ans[++top]=a[j];
        else rep(j,1,mid) ans[++top]=a[j];
        return 1;
    }
    return 0;
}
int main(){
    scanf("%d",&n);if(n%2==0) {puts("NOT POSSIBLE");return 0;}
    scanf("%s",a+1);mid=n/2;
        
    p[0]=1;b=19911103;
    rep(i,1,n) p[i]=p[i-1]*b;
    rep(i,1,n) sum[i]=sum[i-1]*b+(a[i]-'A'+1);
    
    int cnt=0;
    rep(i,1,n){cnt+=judge(i);if(cnt>1) break;}
        
    if(!cnt) puts("NOT POSSIBLE");
    else if(cnt>1) puts("NOT UNIQUE");
    else puts(ans+1); return 0;
}

别人的代码，侵删啊啊啊

#include<cstring>
#include<iostream>
#include<cstdio>
#include<algorithm>
#define rep(i,l,r) for (int i=l;i<=r;i++)
#define down(i,l,r) for (int i=l;i>=r;i--)
#define clr(x,y) memset(x,y,sizeof(x))
#define maxn 2000009
#define p 23333
using namespace std;
typedef unsigned long long ll;
char ans[maxn],s[maxn];
ll h[maxn],bin[maxn],last;
int now,n,mid,anspos;
int read(){
    int x=0,f=1; char ch=getchar();
    while (!isdigit(ch)){
        if (ch=='-') f=-1; ch=getchar();
    }
    while (isdigit(ch)){
        x=x*10+ch-'0'; ch=getchar();
    }
    return x*f;
}
ll get(int l,int r){
    return h[r]-h[l-1]*bin[r-l+1];
}
int judge(int pos){
    ll x,y,z;
    int flag=0;
    if (pos<mid){
        x=get(1,pos-1)*bin[mid-pos]+get(pos+1,mid);
        y=get(mid+1,n);
    }
    else if (pos>mid){
        x=get(1,mid-1);
        y=get(mid,pos-1)*bin[n-pos]+get(pos+1,n);
    }
    else if (pos==mid){
        x=get(1,mid-1);
        y=get(mid+1,n);
    }
    if (x==y){
        if (x==last) return 0;
        last=x;
        int top=0;
        if (pos<=mid) rep(i,mid+1,n) ans[++top]=s[i];
        else rep(i,1,mid-1) ans[++top]=s[i];
        return 1;
    }
    return 0;
}
int main(){
    freopen("3916.in","r",stdin);
    freopen("3916.out","w",stdout);
    n=read(); if (n%2==0) {puts("NOT POSSIBLE"); return 0;}
    scanf("%s",s+1); 
    bin[0]=1; rep(i,1,n) bin[i]=bin[i-1]*p;
    rep(i,1,n) h[i]=h[i-1]*p+s[i];
    mid=(n/2)+1;
    int cnt=0;
    rep(i,1,n) {
        cnt+=judge(i);
        if (cnt>1) break;
    }
    if (!cnt) puts("NOT POSSIBLE");
    else if (cnt>1) puts("NOT UNIQUE");
    else puts(ans+1);
    return 0; 
}