查询在计算机中十分广泛的应用。
- 在字符串或者文本文件中查询关键字，模式匹配，正则表达式。
- 在数组、树、哈希表等数据结构中查询指定数据
- 在数据库中查询
- 在海量非结构文件中查询
- 搜索引擎
模式匹配
模式匹配是数据结构中字符串的一种基本运算，给定一个子串，要求在某个字符串中找出与该子串相同的所有子串，这就是模式匹配。
DFA算法
rust
use std::collections::BTreeSet;
use std::collections::HashMap;
use std::fs::File;
use std::io::prelude::*;
use std::io::BufReader;
use std::str::Chars;
/// 敏感词检测DFA算法（Rust实现，参考Java版实现 https://www.cnblogs.com/shihaiming/p/7048379.html）
/// 由于语言方面的限制，具体实现与Java有一定的差异。
///
lazy_static! {
static ref SENSITIVE_WORD_MAP: HashMap<char, SensitiveWordMap> = {
let set = read_sensitive_word_file();
build_sensitive_word_map(set)
};
}
pub enum MatchType {
MinMatchType, //最小匹配规则
MaxMatchType, //最大匹配规则
}
#[derive(Debug)]
struct SensitiveWordMap {
word: char,
is_end: char,
word_map: Option<HashMap<char, Box<SensitiveWordMap>>>,
}
/// 替换敏感字字符
/// # Examples
/// ```
/// let result = rust_by_example::dfa::replace_sensitive_word("信用卡之家", &MatchType::MinMatchType, '*')
/// assert_eq!(result,"**卡之家");
/// ```
pub fn replace_sensitive_word(txt: &str, match_type: &MatchType, replace_char: char) -> String {
let set: BTreeSet<String> = find_sensitive_word(txt, match_type);
let mut replace_str = String::from(txt);
for word in set {
let len = word.chars().count();
let replace_chars: String = vec![replace_char; len].iter().collect();
replace_str = replace_str.replace(word.as_str(), &replace_chars);
}
replace_str
}
/// 判断文字是否包含敏感字符
///
pub fn is_contains_sensitive_word(txt: &str, match_type: &MatchType) -> bool {
let mut is_contains = false;
let len = txt.chars().count();
let txt_vec: Vec<char> = txt.chars().collect();
let mut i = 0;
while i < len {
let length = check_sensitive_word(txt, i, match_type);
if length > 0 {
is_contains = true;
break;
}
i += 1;
}
is_contains
}
/// 获取文字中的敏感词
///
pub fn find_sensitive_word(txt: &str, match_type: &MatchType) -> BTreeSet<String> {
let mut sensitive_word_set = BTreeSet::<String>::new();
let len = txt.chars().count();
let txt_vec: Vec<char> = txt.chars().collect();
let mut i = 0;
while i < len {
let length = check_sensitive_word(txt, i, match_type);
if length > 0 {
//存在,加入list中
sensitive_word_set.insert(txt_vec[i..i + length].iter().collect());
i += length - 1; //减1的原因，是因为循环会自增
}
i += 1;
}
sensitive_word_set
}
/// 查文字中是否包含检敏感字符,如果存在，则返回敏感词字符的长度，不存在返回0
///
fn check_sensitive_word(txt: &str, begin_index: usize, match_type: &MatchType) -> usize {
let mut match_flag = 0;
let mut last_match_length = 0;
let mut word: char;
let txt_vec: Vec<char> = txt.chars().collect();
let len = txt.len();
if let Some(word) = &txt_vec.get(begin_index) {
if let Some(swm) = SENSITIVE_WORD_MAP.get(word) {
match_flag += 1;
if (*swm).is_end == '1' {
last_match_length = match_flag;
match match_type {
MatchType::MinMatchType => {
return last_match_length;
}
MatchType::MaxMatchType => (),
}
}
//递归查找
let mut j = begin_index + 1;
recursive_find_map(
swm,
&txt_vec,
&mut j,
&mut match_flag,
&mut last_match_length,
match_type,
);
}
}
last_match_length
}
/// 递归查找map
///
fn recursive_find_map(
swm: &SensitiveWordMap,
txt_vec: &[char],
i: &mut usize,
match_flag: &mut usize,
last_match_length: &mut usize,
match_type: &MatchType,
) {
if let Some(word) = txt_vec.get(*i) {
if let Some(wm) = &swm.word_map {
if let Some(next_swm) = wm.get(word) {
*match_flag += 1;
if swm.is_end == '1' {
*last_match_length = *match_flag;
match match_type {
MatchType::MinMatchType => {
return;
}
MatchType::MaxMatchType => (),
}
}
if next_swm.is_end == '1' {
*last_match_length = *match_flag;
match match_type {
MatchType::MinMatchType => {
return;
}
MatchType::MaxMatchType => (),
}
}
if let Some(nwm) = &next_swm.word_map {
if nwm.is_empty() {
*last_match_length = *match_flag;
match match_type {
MatchType::MinMatchType => {
return;
}
MatchType::MaxMatchType => (),
}
}
}
*i += 1;
recursive_find_map(
next_swm,
txt_vec,
i,
match_flag,
last_match_length,
match_type,
);
}
}
}
}
/// 递归地修改map
fn recursive_build_map(map: &mut SensitiveWordMap, chars: &mut Chars, count: &mut usize) {
if let Some(ch) = chars.next() {
*count -= 1;
if let Some(now_map) = map.word_map.as_mut() {
// let contains_key = now_map.contains_key(&ch);
if let std::collections::hash_map::Entry::Vacant(e) = now_map.entry(ch) {
let mut is_end = if *count == 0 { '1' } else { '0' };
let mut swm = SensitiveWordMap {
word: ch,
is_end,
word_map: Some(HashMap::<char, Box<SensitiveWordMap>>::new()),
};
now_map.insert(ch, Box::new(swm));
if let Some(m) = now_map.get_mut(&ch) {
recursive_build_map(&mut *m, &mut *chars, count);
}
} else if let Some(m) = now_map.get_mut(&ch) {
recursive_build_map(&mut *m, &mut *chars, count);
}
}
}
}
/// 读取敏感词库，将敏感词放入HashMap中，构建一个DFA算法模型
/// {
/// '信': SensitiveWordMap {
/// word: '信',
/// is_end: '0',
/// word_map: Some({
/// '用': SensitiveWordMap {
/// word: '用',
/// is_end: '0',
/// word_map: Some({
/// '卡': SensitiveWordMap {
/// word: '卡',
/// is_end: '0',
/// word_map: Some({
/// '套': SensitiveWordMap {
/// word: '套',
/// is_end: '0',
/// word_map: Some({
/// '现': SensitiveWordMap {
/// word: '现',
/// is_end: '1',
/// word_map: Som e({})
/// }
/// })
/// },
/// '代': SensitiveWordMap {
/// word: '代',
/// is_end: '0',
/// word_map: Some({
/// '付': SensitiveWordMap {
/// word: '付',
/// is_end: '1',
/// word_map: Some({})
/// },
/// '还': SensitiveWordMap {
/// word: '还',
/// is_end: '1',
/// word_map: Some({})
/// }
/// })
/// }
/// })
/// }
/// })
/// }
/// })
/// }
///
fn build_sensitive_word_map(set: BTreeSet<String>) -> HashMap<char, SensitiveWordMap> {
let mut sensitive_word_map = HashMap::<char, SensitiveWordMap>::new();
let mut iterator = set.iter();
for key in iterator {
let len = key.chars().count();
let mut count = len;
let mut key_chars = key.chars();
//读取每行的首个字符
if let Some(first_char) = key_chars.next() {
count -= 1;
if let Some(word_map) = sensitive_word_map.get_mut(&first_char) {
//读取下一个字符
recursive_build_map(&mut *word_map, &mut key_chars, &mut count);
} else {
let mut is_end = if len == 1 { '1' } else { '0' };
let mut now_map = SensitiveWordMap {
word: first_char,
is_end,
word_map: Some(HashMap::<char, Box<SensitiveWordMap>>::new()),
};
sensitive_word_map.insert(first_char, now_map);
if let Some(now_map) = sensitive_word_map.get_mut(&first_char) {
recursive_build_map(&mut *now_map, &mut key_chars, &mut count);
}
}
}
}
sensitive_word_map
}
/// 读取敏感词库中的内容，将内容添加到set集合中
fn read_sensitive_word_file() -> BTreeSet<String> {
let mut set = BTreeSet::<String>::new();
match File::open("sensitive-words.txt") {
Ok(f) => {
let reader = BufReader::new(f);
let lines = reader.lines();
for line in lines.map(|x| x.unwrap()) {
println!("{}", line);
set.insert(line);
}
}
Err(e) => panic!("can't open this file :{}", e),
}
set
}
#[test]
fn read_file() {
let str_vec = vec![
"花呗信用卡代还OK套现",
"套花呗分期代付",
"马上套现信用卡",
"期货套利",
"空手套白狼",
"守信用卡脖子",
"坚定信心,同舟共济,科学防治,精准施策",
"D+1还是T+1秒到结算免结算费",
];
println!("find_sensitive_word MaxMatchType......");
for str in &str_vec {
let set = find_sensitive_word(str, &MatchType::MaxMatchType);
println!("{} --> {:?}", str, set);
}
println!("find_sensitive_word MinMatchType......");
for str in &str_vec {
let set = find_sensitive_word(str, &MatchType::MinMatchType);
println!("{} --> {:?}", str, set);
}
println!("is_contains_sensitive_word......");
for str in &str_vec {
let is_contains = is_contains_sensitive_word(str, &MatchType::MinMatchType);
println!("{} is contains sensitive words : {}", str, is_contains);
}
println!("replace_sensitive_word......");
for str in &str_vec {
let replace_str = replace_sensitive_word(str, &MatchType::MinMatchType, '*');
println!("{} --> {}", str, replace_str);
}
let result = replace_sensitive_word("信用卡之家", &MatchType::MinMatchType, '*');
assert_eq!(result, "**卡之家");
}
#[test]
fn sub_str() {
//实现类似Java String.substring()的功能，注意并不是适用于所有的字符。
let str = String::from("hello world");
let char_vec: Vec<char> = str.chars().collect();
let sub_str: String = char_vec[0..5].iter().collect();
println!("sub_str:{}", sub_str);
//不能使用上述代码进行截取子字符串的字符
for c in "नमस्ते".chars() {
println!("{}", c);
}
}
#[test]
fn set_iter() {
let mut b_tree_set = BTreeSet::<String>::new();
b_tree_set.insert(String::from("A"));
b_tree_set.insert(String::from("B"));
b_tree_set.insert(String::from("C"));
b_tree_set.insert(String::from("D"));
b_tree_set.insert(String::from("E"));
for val in &b_tree_set {
println!("{}", val);
}
let rm_key = String::from("C");
b_tree_set.remove(&rm_key);
println!("b_tree_set has {} items", b_tree_set.len());
println!("using VSCode coding rust program is greate");
}KMP匹配算法
rust
/// https://github.com/TheAlgorithms/Rust/blob/master/src/string/knuth_morris_pratt.rs
pub fn knuth_morris_pratt(st: String, pat: String) -> Vec<usize> {
if st.is_empty() || pat.is_empty() {
return vec![];
}
let string = st.into_bytes();
let pattern = pat.into_bytes();
// build the partial match table
let mut partial = vec![0];
for i in 1..pattern.len() {
let mut j = partial[i - 1];
while j > 0 && pattern[j] != pattern[i] {
j = partial[j - 1];
}
partial.push(if pattern[j] == pattern[i] { j + 1 } else { j });
}
// and read 'string' to find 'pattern'
let mut ret = vec![];
let mut j = 0;
for (i, &c) in string.iter().enumerate() {
while j > 0 && c != pattern[j] {
j = partial[j - 1];
}
if c == pattern[j] {
j += 1;
}
if j == pattern.len() {
ret.push(i + 1 - j);
j = partial[j - 1];
}
}
ret
}正则表达式
驼峰命名转为蛇形命名
bash
echo "camelToSnakeName" | sed 's/\([a-z0-9]\)\([A-Z]\)/\1_\2/g' | tr '[:lower:]' '[:upper:]'
rust
use itertools::Itertools;
use regex::Captures;
use regex::NoExpand;
use regex::Regex;
use std::collections::HashMap;
lazy_static! {
//驼峰命名
static ref CAMEL_TO_SNAKE1: Regex = Regex::new(r"(.)([A-Z][a-z]+)").unwrap();
static ref CAMEL_TO_SNAKE2: Regex = Regex::new(r"([a-z0-9])([A-Z])").unwrap();
}
/// 驼峰命名转为蛇形命名
pub fn camel_to_snake(origin: &str) -> String {
let result0 = CAMEL_TO_SNAKE1.replace_all(origin, |caps: &Captures| {
format!("{}_{}", &caps[1], &caps[2])
});
let result = CAMEL_TO_SNAKE2.replace_all(&result0, |caps: &Captures| {
format!("{}_{}", &caps[1], &caps[2])
});
result.to_uppercase()
}
/// 驼峰命名转为帕斯卡命名法
pub fn snake_to_pascal(origin: &str) -> String {
// origin.split('_');
let word_vec: Vec<&str> = origin.split('_').collect();
//每个单词首字母大写
word_vec
.iter()
.map(|&word| {
let mut chars = word.chars();
match chars.next() {
Some(ch) => ch.to_uppercase().collect::<String>() + chars.as_str(),
None => String::new(),
}
})
.join("")
}
/// 蛇形命名转驼峰命名
pub fn snake_to_camel(s: &str) -> String {
let result = snake_to_pascal(s);
let mut chars = result.chars();
match chars.next() {
Some(ch) => ch.to_lowercase().collect::<String>() + chars.as_str(),
None => String::new(),
}
}
#[test]
fn fileds() {
let fileds_vec = vec!["FalconHeavyRocket", "HTTPResponseCodeXYZ"];
fileds_vec.iter().for_each(|&filed| {
let result = camel_to_snake(filed);
println!("{}", result);
});
let columns_vec = vec!["falcon_heavy_rocket", "http_response_code_xyz"];
columns_vec.iter().for_each(|&column| {
let result = snake_to_pascal(column);
println!("{}", result);
});
let columns_vec = vec!["falcon_heavy_rocket", "http_response_code_xyz"];
columns_vec.iter().for_each(|&column| {
let result = snake_to_camel(column);
println!("{}", result);
});
}经典查询算法
查询算法:二分查找、哈希查找、二叉树查找、、
二分查找
rust
/// 力扣（704. 二分查找) https://leetcode-cn.com/problems/binary-search/
pub fn search(nums: Vec<i32>, target: i32) -> i32 {
// target在[left,right]中查找
let len = nums.len();
let mut left = 0;
let mut right = len - 1;
let mut pivot;
while left <= right {
pivot = left + (right - left) / 2;
// 注意usize的范围和nums的下标范围
if nums[pivot] == target {
return pivot as i32;
}
if target < nums[pivot] {
if pivot == 0 {
break;
}
right = pivot - 1;
} else {
if pivot == len - 1 {
break;
}
left = pivot + 1;
}
}
-1
}二叉树查找
rust
//! 二叉树
//! https://leetcode-cn.com/tag/binary-tree/problemset/
use std::cell::RefCell;
use std::cmp::max;
use std::collections::VecDeque;
use std::rc::Rc;
#[derive(Debug, PartialEq, Eq)]
pub struct TreeNode {
pub val: i32,
pub left: Option<Rc<RefCell<TreeNode>>>,
pub right: Option<Rc<RefCell<TreeNode>>>,
}
impl TreeNode {
#[inline]
pub fn new(val: i32) -> Self {
TreeNode {
val,
left: None,
right: None,
}
}
/// 树的深度：也称为树的高度，树中所有结点的层次最大值称为树的深度
pub fn get_height(root: &Option<Rc<RefCell<TreeNode>>>) -> i32 {
fn dfs(root: &Option<Rc<RefCell<TreeNode>>>) -> i32 {
match root {
None => 0,
Some(node) => {
let node = node.borrow_mut();
1 + max(dfs(&node.left), dfs(&node.right))
}
}
}
dfs(root)
}
}
/// 230. 二叉搜索树中第K小的元素 https://leetcode.cn/problems/kth-smallest-element-in-a-bst/
pub fn kth_smallest(root: Option<Rc<RefCell<TreeNode>>>, k: i32) -> i32 {
fn traverse(root: Option<Rc<RefCell<TreeNode>>>, counter: &mut Vec<i32>) {
if let Some(node) = root {
traverse(node.borrow_mut().left.take(), counter);
counter.push(node.borrow_mut().val);
traverse(node.borrow_mut().right.take(), counter);
}
}
let mut counter = vec![];
traverse(root, &mut counter);
counter[(k - 1) as usize]
}