P3667 [USACO17OPEN]Bovine Genomics

二分 + trie树大常数水过. 其实是一道字符串hash.

#include <cstdio>
#include <stack>
#include <cstring>
#include <cassert>
#include <iostream>
#include <algorithm>
using namespace std;
const int MAXN = 5e2 + 20;

int N, M;
char str[MAXN << 1][MAXN];

inline int getnum(char ch){
    switch (ch){
        case 'A': return 0;
        case 'T': return 1;
        case 'C': return 2;
        case 'G': return 3;
    }
}

namespace trie
{
    struct Node
    {
        bool ended;
        Node *ch[4];
        Node() : ended(false) {}
    }pool[MAXN * MAXN], *pit = pool, root, null;

    int cnt = 1;

    inline Node *newnode(){
        if(cnt < (MAXN * MAXN)) return ++cnt, new(pit++) Node();
        return new Node();
    }

    Node *insert(Node *cur, char s[], int p){
        if(!cur) cur = newnode();
        if(!p) return cur->ended = true, cur;
        cur->ch[getnum(*s)] = insert(cur->ch[getnum(*s)], s + 1, p - 1);
        return cur;
    }

    bool query(Node *cur, char s[], int p){
        if(!cur) return false;
        if(!p) return cur->ended;
        return query(cur->ch[getnum(*s)], s + 1, p - 1);
    }

    void init(){
        for(int i = 0; i < 4; i++) null.ch[i] = NULL;
        null.ended = false;
        for(int i = 0; i < cnt; i++) pool[i] = null;
        pit = pool, cnt = 1; root = null;
    }
}

bool check(int x){
    using namespace trie;
       
    for(int l = 1; l <= (M - x + 1); l++){
    	init();
        for(int i = 1; i <= N; i++) insert(&root, str[i] + l, x);
        bool flag = false;
        for(int i = N + 1; i <= (N << 1); i++) 
            if(query(&root, str[i] + l, x)) {
                flag = true; break;
            }
        if(!flag) return true;
    }

    return false;
}

int main()
{
    //freopen("p3667.in", "r", stdin);
    cin>>N>>M;
    for(int i = 1; i <= (N << 1); i++) scanf(" %s", str[i] + 1);

    int l = 0, r = M;
    while(l < r){
        int mid = (l + r) >> 1;
        if(check(mid)) r = mid;
        else l = mid + 1;
    } 
    cout<<l<<endl;
    return 0;
}