后缀字典序中二分找查询串区间

Posted 2020-10-17 mxzf0213

bool cmp1(int pos,char *p)
{
    pos=sa[pos];
    int len1=n-pos+1,len2=now,l=min(len1,len2);
    int flag=strncmp(a+pos,p,l);
    return flag>0||(flag==0&&len1>=len2);
}
bool cmp2(int pos,char *p)
{
    pos=sa[pos];
    int len1=n-pos+1,len2=now,l=min(len1,len2);
    int flag=strncmp(a+pos,p,l);
    return flag<=0;
}
bool ok(int pos,char *p)
{
    pos=sa[pos];
    int len=n-pos+1;
    return len>=now&&strncmp(a+pos,p,now)==0;
}
//main函数
int ql=1,qr=n,ans1=n+1,ans2=0;
while(ql<=qr)
{
    int mid=ql+qr>>1;
    if(cmp1(mid,b))ans1=mid,qr=mid-1;
    else ql=mid+1;
}
ql=1,qr=n;
while(ql<=qr)
{
     int mid=ql+qr>>1;
     if(cmp2(mid,b))ans2=mid,ql=mid+1;
     else qr=mid-1;
}
if(ans1<=ans2&&ok(ans1,b)&&ok(ans2,b))
{
     qu[l-1].pb(node{ans1,ans2,-i});
     qu[r-now+1].pb(node{ans1,ans2,i});
}