【LOJ】#2291. 「THUSC 2016」补退选

题解

在trie树上开vector记录一下这个前缀出现次数第一次达到某个值的下标，以及记录一下现在这个前缀有多少个

为什么thusc有那么水的题……是为了防我这种cai ji爆零么= =

代码

#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cstring>
//#define ivorysi
#define pb push_back
#define eps 1e-12
#define space putchar(' ')
#define enter putchar('\n')
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define mo 974711
using namespace std;
typedef long long int64;
typedef double db;
struct node {
    vector<int> v;
    int cnt;
    int nxt[10];
    node() {cnt = 0;v.clear();memset(nxt,0,sizeof(nxt));}
}tr[6000005];
int rt = 1,nodecnt = 1,Q;
char s[65];
void Insert(int id,char *str,int on) {
    int p = 1,L = strlen(str + 1);
    for(int i = 1 ; i <= L ; ++i) {
	if(!tr[p].nxt[str[i] - 'a']) {
	    tr[p].nxt[str[i] - 'a'] = ++nodecnt;
	}
	p = tr[p].nxt[str[i] - 'a'];
	tr[p].cnt += on;
	if(tr[p].cnt > tr[p].v.size()) tr[p].v.pb(id);
    }
}
int Query(char *str,int x) {
    int p = 1,L = strlen(str + 1);
    for(int i = 1 ; i <= L ; ++i) {
	if(!tr[p].nxt[str[i] - 'a']) return -1;
	p = tr[p].nxt[str[i] - 'a'];
    }
    if(tr[p].v.size() - 1 < x) return -1;
    return tr[p].v[x];
}
void Solve() {
    scanf("%d",&Q);
    int K,ans = 0,a,b,c;
    for(int i = 1 ; i <= Q ; ++i) {
	scanf("%d",&K);scanf("%s",s + 1);
	if(K == 1) Insert(i,s,1);
	else if(K == 2) Insert(i,s,-1);
	else {
	    scanf("%d%d%d",&a,&b,&c);
	    int t = (1LL * abs(ans) * a + b) % c;
	    printf("%d\n",ans = Query(s,t));
	}
    }
}
int main() {
#ifdef ivorysi
    freopen("f1.in","r",stdin);
#endif
    Solve();
    return 0;
}