A. Yet Another Problem with Strings 分块 + hash

http://codeforces.com/gym/101138/problem/A

 

感觉有一种套路就是总长度 <= 某一个数的这类题，大多可以分块

首先把集合串按长度分块，对于每一个询问串，

在 > magic的big集合里，因为最多sqrtn个，可以暴力枚举每一个，然后暴力枚举询问串的每一个长度是其的子串，判断是否相等

在 <= magic的small集合里，枚举每一个长度是magic, magic-1, magic-2, magic-3........1的字符串，然后看看是否在small集合里存在

small集合用unordermap保存即可。

 ps

判断map是否存在一个元素，用mp.find

不然用mp[]每次都会生成一个节点，然后MLE， 清空用mp.erase

不然Mp.find是true的

#include <bits/stdc++.h>
#define IOS ios::sync_with_stdio(false)
using namespace std;
#define inf (0x3f3f3f3f)
typedef unsigned long long int ULL;

const int seed = 131;
const int maxn = 200000 + 20;
struct Node {
    ULL hs;
    int lenstr;
    Node(ULL _hs, int _lenstr) {
        hs = _hs, lenstr = _lenstr;
    }
    bool operator < (const Node & rhs) const {
        if (hs != rhs.hs) return hs > rhs.hs;
        else return lenstr > rhs.lenstr;
    }
};
vector<Node> all;
set<Node> ss;
unordered_map<ULL, bool> mp;
char str[maxn];
int magic;
set<Node> :: iterator it;
void addchar(int id, char ch) {
//    set<Node> :: iterator it;
    if (all[id].lenstr > magic) {
        ss.erase(ss.find(all[id]));
        all[id].lenstr++;
        all[id].hs = all[id].hs * seed + ch;
        ss.insert(all[id]);
    } else {
        if (all[id].lenstr == magic) {
            mp.erase(all[id].hs);
//            mp[all[id].hs] = false;
            all[id].lenstr++;
            all[id].hs = all[id].hs * seed + ch;
            ss.insert(all[id]);
        } else {
            mp.erase(all[id].hs);
            all[id].lenstr++;
            all[id].hs = all[id].hs * seed + ch;
            mp[all[id].hs] = true;
        }
    }
}
ULL po[maxn];
ULL sum[maxn];
int last_yes;
bool ok() {
    int lenstr = strlen(str + 1);
    for (int i = 1; i <= lenstr; ++i) {
        str[i] = (str[i] - 'a' + last_yes) % 26 + 'a';
        sum[i] = sum[i - 1] * seed + str[i];
    }
    for (it = ss.begin(); it != ss.end(); ++it) {
        int len = it->lenstr;
        for (int j = len; j <= lenstr; ++j) {
            if (it->hs == sum[j] - po[len] * sum[j - len]) return true;
        }
    }
    for (int i = 1; i <= lenstr; ++i) {
        for (int c = 1; c <= magic && c <= i; ++c) {
            if (mp.find(sum[i] - po[c] * sum[i - c]) != mp.end()) return true;
        }
    }
    return false;
}

void work() {
    int n, q;
    scanf("%d%d", &n, &q);
    magic = (int)sqrt(n * 1.0);
    for (int i = 1; i <= n; ++i) {
        scanf("%s", str + 1);
        ULL hashVal = 0;
        int lenstr = strlen(str + 1);
        for (int j = 1; j <= lenstr; ++j) {
            hashVal = hashVal * seed + str[j];
        }
        if (lenstr > magic) ss.insert(Node(hashVal, lenstr));
        else {
            mp[hashVal] = true;
        }
        all.push_back(Node(hashVal, lenstr));
    }
    last_yes = 0;
    for (int i = 0 ; i < q; ++i) {
        int op;
        scanf("%d", &op);
        if (op == 2) {
            int index, ch;
            scanf("%d%d", &index, &ch);
            addchar((index + last_yes) % n, (ch + last_yes) % 26 + 'a');
        } else {
            scanf("%s", str + 1);
            if (ok()) {
                printf("YES\n");
                last_yes = i;
            } else printf("NO\n");
        }
    }
}

int main() {
#ifdef local
    freopen("data.txt", "r", stdin);
//    freopen("data.txt", "w", stdout);
#endif
    po[0] = 1;
    for (int i = 1; i <= maxn - 2; ++i) po[i] = po[i - 1] * seed;
    work();
    return 0;
}