Watto and Mechanism 【CodeForces - 514C】【字典树～Trie】

题目链接

---

  好久不敲字典树了，都差点忘记了，这道题就是字典树加上DFS搜素即可，dfs搜的时候还要加上条件，就是是否有改变，且最后是否等长，且要刚好改变一个字符。

---

  我用val判断是否是终点，在用nex[]数组往下推。

#include <iostream>
#include <cstdio>
#include <cmath>
#include <string>
#include <cstring>
#include <algorithm>
#include <limits>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#define lowbit(x) ( x&(-x) )
#define pi 3.141592653589793
#define e 2.718281828459045
using namespace std;
typedef unsigned long long ull;
typedef long long ll;
const int maxN=6e5+5;
int N, M;
char s[maxN];
struct Trie
{
    int val;        //终点判断
    Trie *nex[3];
    Trie()
    {
        val=0;
        memset(nex, 0, sizeof(nex));
    }
};
Trie *root = new Trie;
void Creat_trie(Trie *rt, int len)
{
    if(s[len]!='\0')
    {
        if(rt->nex[s[len] - 'a'] == 0)
        {
            rt->nex[s[len] - 'a'] = new Trie;
        }
        Creat_trie(rt->nex[s[len] - 'a'], len+1);
    }
    else rt->val=1;
}
bool dfs(Trie *rt, int len, int rest)
{
    if(s[len+1] == '\0')
    {
        if(rest==0 && rt->val==1) return true;
        else return false;
    }
    if(rest == 1)
    {
        if(rt->nex[s[len+1]-'a']!=0 && dfs(rt->nex[s[len+1]-'a'], len+1, 1)) return true;
        for(int i=0; i<3; i++)
        {
            if(i != s[len+1]-'a' && rt->nex[i]!=0 && dfs(rt->nex[i], len+1, 0)) return true;
        }
    }
    else
    {
        if(rt->nex[s[len+1]-'a']!=0 && dfs(rt->nex[s[len+1]-'a'], len+1, 0)) return true;
    }
    return false;
}
int main()
{
    scanf("%d%d", &N, &M);
    for(int i=1; i<=N; i++)
    {
        getchar();
        scanf("%s", s+1);
        Creat_trie(root, 1);
    }
    for(int i=1; i<=M; i++)
    {
        scanf("%s", s+1);
        if(dfs(root, 0, 1)) printf("YES\n");
        else printf("NO\n");
    }
    return 0;
}