题目链接:牛客--接头密匙




该题是一个很显然的前缀树问题,只需要构建a中所有数组对应的前缀树,之后求b所处前缀个数即可。关于前缀树的构建,可以观看左老师算法讲解045的视频,简单来讲就是用特殊字符将实际数据隔开,同时将实际数据离散化。示例题解如下:
cpp
class Solution {
private:
static constexpr int N = 1e6 + 1;
vector<vector<int>> trie = vector<vector<int>>(N,
vector<int>(12)); // 0 - 9 & '-' & '#'
vector<int> passArr = vector<int>(N);
vector<int> endArr = vector<int>(N);
int cnt;
int getPath(char c) {
if (c == '-') {
return 10;
}
if (c == '#') {
return 11;
}
return c - '0';
}
void buildTrie() {
cnt = 1;
}
void reBuildTrie() {
for (int i = 0; i < cnt; ++i) {
fill(&trie[i][0], &trie[i][0] + 12, 0);
passArr[i] = 0;
endArr[i] = 0;
}
}
void insert(const string& word) {
int cur = 1, path;
passArr[cur]++;
for (char c : word) {
path = getPath(c);
if (trie[cur][path] == 0) {
trie[cur][path] = ++cnt;
}
cur = trie[cur][path];
passArr[cur]++;
}
endArr[cur]++;
}
int prefixCount(const string& word) {
int cur = 1, path;
for (char c : word) {
path = getPath(c);
if (trie[cur][path] == 0) {
return 0;
}
cur = trie[cur][path];
}
return passArr[cur];
}
public:
vector<int> countConsistentKeys(vector<vector<int> >& b,
vector<vector<int> >& a) {
// 建立前缀树
buildTrie();
for (int i = 0; i < a.size(); ++i) {
// a[i] = vector<int>
string s = "";
for (int j = 1; j < a[i].size(); j++) {
s = s + std::to_string(a[i][j] - a[i][j - 1]) + "#";
}
insert(s);
}
vector<int> ans;
// 搜索前缀树
for (int i = 0; i < b.size(); ++i) {
// b[i] = vector<int>
string pre = "";
for (int j = 1; j < b[i].size(); ++j) {
pre = pre + std::to_string(b[i][j] - b[i][j - 1]) + "#";
}
ans.push_back(prefixCount(pre));
}
reBuildTrie();
return ans;
}
};