hdu 5790 Prefix(trie+主席树,好题)

2019-11-08 02:46:15

字体：大中小

来源：转载

供稿：网友

题目链接

PRefix

Time Limit: 2000/4000 MS (java/Others) Memory Limit: 65536/65536 K (Java/Others)Total Submission(s): 791 Accepted Submission(s): 226Problem DescriptionAlice gets N strings. Now she has Q questions to ask you. For each question, she wanna know how many different prefix strings between Lth and Rth strings. It's so easy right? So solve it! InputThe input contains multiple test cases.For each test case, the first line contains one integer N(1≤N≤100000). Then next N lines contain N strings and the total length of N strings is between 1 and 100000. The next line contains one integer Q(1≤Q≤100000). We define a specail integer Z=0. For each query, you get two integer L, R(0=<L,R<N). Then the query interval [L,R] is [min((Z+L)%N,(Z+R)%N)+1,max((Z+L)%N,(Z+R)%N)+1]. And Z change to the answer of this query. OutputFor each question, output the answer. Sample Input

3abcababaa30 20 11 1 Sample Output763 AuthorZSTU Source2016 Multi-University Training Contest 5 
参考题解
题意：给你n个字符串，问你第L个字符串到R个字符串中不同前缀的个数，且强制在线。
思路：这题和之前d-query这题很相似，那题问的是区间内不同数的种类。这题问的是不同前缀个数，所以我们可以先把所有的字符串插入到Trie树中，然后每次插入维护每一个节点最后被遍历到的时刻，然后用主席树维护下就行了。
听说也可以hash每个前缀，然后再用主席树维护。
#include<iostream>#include<cstdio>#include<algorithm>#include<cstring>#include<vector>#include<queue>#include<stack>using namespace std;#define rep(i,a,n) for (int i=a;i<n;i++)#define per(i,a,n) for (int i=n-1;i>=a;i--)#define pb push_back#define fi first#define se secondtypedef vector<int> VI;typedef long long ll;typedef pair<int,int> PII;const int inf=0x3fffffff;const ll mod=1000000007;const int maxn=1e5+100;int a[maxn][27];//int cnt=0,tot=0,n;int root[maxn],p[maxn]; //struct node{    int l,r,sum;}T[maxn*40];void update(int l,int r,int &x,int y,int pos,int val){    T[++cnt]=T[y],x=cnt,T[cnt].sum+=val;    if(l==r) return;    int m=(l+r)/2;    if(pos<=m) update(l,m,T[x].l,T[y].l,pos,val);    else update(m+1,r,T[x].r,T[y].r,pos,val);}char s[maxn];void insert(int x){    int l=strlen(s);    int u=0;    rep(i,0,l)    {        if(!a[u][s[i]-'a'])        {            a[u][s[i]-'a']=++tot;            p[tot]=x;            if(i) update(1,n,root[x],root[x],x,1);            else update(1,n,root[x],root[x-1],x,1);                    }        else        {            int t=p[a[u][s[i]-'a']];            if(i) update(1,n,root[x],root[x],t,-1);            else update(1,n,root[x],root[x-1],t,-1);            update(1,n,root[x],root[x],x,1);            p[a[u][s[i]-'a']]=x;        }        u=a[u][s[i]-'a'];    }}int query(int l,int r,int x,int pos){    if(l==r) return T[x].sum;    int m=(l+r)/2;    if(pos<=m) return query(l,m,T[x].l,pos)+T[T[x].r].sum;    else return query(m+1,r,T[x].r,pos);}int main(){        while(~scanf("%d",&n))    {        memset(a,0,sizeof(a));        tot=0,cnt=0;        memset(root,0,sizeof(root));        memset(T,0,sizeof(T));        memset(p,0,sizeof(p));        rep(i,1,n+1)        {            scanf("%s",s);            insert(i);        }        int q,z=0;        scanf("%d",&q);        while(q--)        {            int l,r;            scanf("%d%d",&l,&r);            l=(l+z)%n,r=(r+z)%n;            l++,r++;            if(l>r) swap(l,r);            z=query(1,n,root[r],l);//            printf("%d/n",z);        }    }    return 0;}

上一篇：基础练习回形取数

下一篇：基础练习龟兔赛跑预测