字符串多模匹配---最左优先

#pragma once

#include <string>

#include <unordered_map>

#include <vector>

struct Node{

int fail;

std::string change_word;

std::string word;

using TransMap = std::unordered_map<char, int>;

TransMap trans;

};

class ChangeWordTrie {

public:

inline void Init(int capacity = 100000) {

trie_.reserve(capacity);

rt_ = NewNode();

}

void Insert(const std::string& text, const std::string& word) {

int u = rt_;

for (size_t i = 0; i < text.size(); ++i) {

char c = text[i];

if (!trie_[u].trans.count(c)) trie_[u].trans[c] = NewNode();

u = trie_[u].trans[c];

}

trie_[u].word = word;

trie_[u].change_word = text;

}

void Build() {

std::queue<int> Q;

trie_[rt_].fail = rt_;

for (const auto& p : trie_[rt_].trans) {

char c = p.first;

int nxt = trie_[rt_].trans[c];

trie_[nxt].fail = rt_;

Q.push(nxt);

}

// BFS 构建 Trie图

while (!Q.empty()) {

int u = Q.front();

Q.pop();

for (const auto& p : trie_[u].trans) {

char c = p.first;

int u_fail = trie_[u].fail;

int nxt = trie_[u].trans[c];

while (u_fail != rt_ && !trie_[u_fail].trans.count(c)) {

u_fail = trie_[u_fail].fail;

}

trie_[nxt].fail = trie_[u_fail].trans.count(c) ? trie_[u_fail].trans[c] : rt_;

Q.push(nxt);

}

}

}

std::string Search(const std::string& text) {

/* TODO : 通过合并优化last数组遍历单词节点的效率 保证复杂度 */

std::string result = text;

int u = rt_;

int change = 0; //替换变种词后源字符串长度的改变

for (size_t i = 0; i < text.size(); ++i) {

char c = text[i];

while (u != rt_ && !trie_[u].trans.count(c)) {

u = trie_[u].fail;

}

if (trie_[u].trans.count(c)) u = trie_[u].trans[c];

if (!trie_[u].word.empty()) {

result = result.replace(i - trie_[u].change_word.length() + 1 - change, trie_[u].change_word.length(), trie_[u].word);

change += trie_[u].change_word.length() - trie_[u].word.length();

u = rt_;

}

}

return result;

}

private:

int rt_; // Root of trie

std::vector<Node> trie_;

int NewNode() {

trie_.emplace_back();

return trie_.size() - 1;

}

};