2019 上海网络赛G 手写哈希map+字符串hash

https://nanti.jisuanke.com/t/41415

因为对于询问$\sum |s|<=1e5$,因此$|s|$的种类数$<=\sqrt{1e5}$

我们分组标记,就变成了$\sqrt{1e5}$次询问了,我们暴力去跑,

复杂度$1e5\sqrt{1e5}*hashmap$

暴力+哈希+$unordermap$计数,嗯,果然TLE了

然后手写一个$hashmap$,跑的飞快...

#include<bits/stdc++.h>
#define ull unsigned long long
#define fi first
#define se second
#define mp make_pair
#define pii pair<ull,int>
#define rep(ii,a,b) for(int ii=a;ii<=b;++ii)
using namespace std;
const int maxn=1e5+10,maxm=3e5+17;
const ull mod=1e9+7;
int casn,n,m;
char a[maxn],b[maxn];
ull pw[200];
int len[20010],ans[20010];
vector<pii> ask[maxn];
class hash_map{public:
  struct node{ull u;int v,next;}e[maxm<<1];
  int head[maxm],nume,numk,id[maxm];
  int& operator[](ull u) {
    int hs=u%maxm;
    for(int i=head[hs];i;i=e[i].next)
      if(e[i].u==u) return e[i].v;
    if(!head[hs])id[++numk]=hs;
    return e[++nume]=(node){u,0,head[hs]},head[hs]=nume,e[nume].v;
  }
  void clear(){
    rep(i,0,numk)head[id[i]]=0;
    numk=nume=0;
  }
}cnt;
int main(){
  pw[0]=1;rep(i,1,131) pw[i]=pw[i-1]*mod;
  ull base1=pw[130],base2=pw[131];
  cin>>casn;
  while(casn--){
    cin>>(a+1)>>m;
    int n=strlen(a+1);
    rep(i,1,m){
      cin>>(b+1);
      len[i]=strlen(b+1);
      ull hs=base1*b[1]+base2*b[len[i]];
      rep(j,2,len[i]-1) hs+=pw[b[j]];
      ask[len[i]].emplace_back(mp(hs,i));
    }
    int k=unique(len+1,len+1+m)-len-1;
    rep(i,1,k){
      int l=len[i];
      ull hs=0;
      rep(j,2,l-1) hs+=pw[a[j]];
      rep(j,1,n-l+1){
        ++cnt[hs+base1*a[j]+base2*a[j+l-1]];
        hs+=pw[a[j+l-1]]-pw[a[j+1]];
      }
      for(auto &j:ask[l]) ans[j.se]+=cnt[j.fi];
      cnt.clear();
      ask[l].clear();
    }
    rep(i,1,m) {
      cout<<ans[i]<<‘\n‘;
      ans[i]=0;
    }
  }
}

原文地址：https://www.cnblogs.com/nervendnig/p/11525346.html