1 second
256 megabytes
standard input
standard output
Sereja has two sequences a and b and number p. Sequence a consists of n integers a1, a2, ..., an. Similarly, sequence b consists of mintegers b1, b2, ..., bm. As usual, Sereja studies the sequences he has. Today he wants to find the number of positions q (q + (m - 1)·p ≤ n; q ≥ 1), such that sequence b can be obtained from sequence aq, aq + p, aq + 2p, ..., aq + (m - 1)p by rearranging elements.
Sereja needs to rush to the gym, so he asked to find all the described positions of q.
The first line contains three integers n, m and p (1 ≤ n, m ≤ 2·105, 1 ≤ p ≤ 2·105). The next line contains n integers a1, a2, ..., an (1 ≤ ai ≤ 109). The next line contains m integers b1, b2, ..., bm (1 ≤ bi ≤ 109).
In the first line print the number of valid qs. In the second line, print the valid values in the increasing order.
5 3 1 1 2 3 2 1 1 2 3
2 1 3
6 3 2 1 3 2 2 3 1 1 2 3
2 1 2
题意:很容易理解。
分析:离散化->用hash进行线性求解
比赛的时候没有做出来,后来看了别人的思路,然后自己敲了遍代码,贡献了一次超时和两次Runtime Error,不过从中也得到一些收获,题目中a数组和b数组的元素范围为1<=ai,bi<=10^9,此范围比较大,开数组进行hash不好弄,所以第一步就是离散化,离散化之后就是hash进行求解,实践复杂度为线性的,具体看代码实现。
代码实现:
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std; int n,m,p,total,flag,now;
int a[],b[],c[],all[],visited[]; void hebing()//合并成一个数组,全部存在c数组里
{
int i,j,x;
total=;
for(i=;i<=n;i++)
c[++total]=a[i];
for(i=;i<=m;i++)
c[++total]=b[i];
sort(c+,c++total);
x=;
for(i=;i<=total;i++)//去重
if(i==||c[i]!=c[i-])
c[++x]=c[i];
total=x;
} int find(int x)//二分查找x处在c数组中的位置
{
int l=,r=total+,mid;
while(l<=r)
{
mid=(l+r)>>;
if(c[mid]==x)
return mid;
else if(c[mid]>x)
r=mid-;
else
l=mid+;
}
} void lisanhua()//对a数组和b数组进行离散化
{
int i;
for(i=;i<=n;i++)
a[i]=find(a[i]);
for(i=;i<=m;i++)
b[i]=find(b[i]);
} void init()
{
int i;
flag=;
memset(all,,sizeof(all));
for(i=;i<=m;i++)//哈希处理b数组的情况
{
if(all[b[i]]==)
flag++;
all[b[i]]++;
}
} void add(int x)
{
visited[x]++;
if(visited[x]==all[x])
now++;
} void del(int x)
{
visited[x]--;
if(visited[x]+==all[x])
now--;
} void solve()
{
int res[],num=,i,j,k;
for(i=;i<=p;i++)//因为相隔为p,所以只需枚举1-p,然后对每一种序列滚动过去
{
if((i+(long long)(m-)*p)<=n)//因为(m-1)*p已经超过int型,所以要强制转换成long long
{ //否则就会出现Runtime Error
now=;
for(j=;j<m;j++)
add(a[i+j*p]);
if(now==flag)
res[num++]=i;
for(j=i+p;(j+(long long)(m-)*p)<=n;j=j+p)//滚动过去
{
del(a[j-p]);
add(a[j+(m-)*p]);
if(now==flag)
res[num++]=j;
}
for(k=;k<m;k++)//把加了的删掉,开始我用了memset(visited,0,sizeof(visited));
del(a[j-p+k*p]);//然后果断超时了
}
}
printf("%d\n",num);
sort(res,res+num);
for(i=;i<num;i++)
if(i!=num-)
printf("%d ",res[i]);
else
printf("%d\n",res[i]);
} int main()
{
int i,j;
scanf("%d%d%d",&n,&m,&p);
{
for(i=;i<=n;i++)
scanf("%d",&a[i]);
for(i=;i<=m;i++)
scanf("%d",&b[i]);
hebing();
lisanhua();
init();
solve();
}
return ;
}