POJ 2758 Checking the Text（Hash+二分答案）

#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std; 
const int N=60000,base=233;
typedef long long ll;
int len,n,m,pos[N],x,y;
ll hash[N],p[N];
char s[N],op[10];
void Build(int x){for(int i=x;i<=len;i++)hash[i]=hash[i-1]*base+s[i];}  
ll get_hash(int L,int R){return hash[R]-hash[L-1]*p[R-L+1];}
int query(int x,int y){  
    int l=0,r=len-max(x,y)+1;  
    while(l<=r){  
        int mid=l+r>>1;  
        if(get_hash(x,x+mid-1)==get_hash(y,y+mid-1))l=mid+1;  
        else r=mid-1;  
    }return r;  
} 
int main(){
    for(int i=p[0]=1;i<N;i++)p[i]=p[i-1]*base;
    scanf("%s",s+1); n=len=strlen(s+1);
    scanf("%d",&m); Build(1);
    for(int i=1;i<=n;i++)pos[i]=i;
    for(int i=1;i<=m;i++){
        scanf("%s",op);
        if(op[0]==‘I‘){
            scanf("%s%d",op,&x);
            if(x>len)x=len+1;
            memcpy(s+x+1,s+x,(len-x+1)*sizeof(char));
            s[x]=op[0];
            for(int j=n;j>=1;j--){
                if(pos[j]>=x)pos[j]++;
                else break;
            }len++; Build(x);
        }else{
            scanf("%d%d",&x,&y);
            printf("%d\n",query(pos[x],pos[y]));
        }
    }return 0;
}