74 lines
2.6 KiB
Rust
74 lines
2.6 KiB
Rust
use std::collections::HashMap;
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fn bf(primary: &str, pattern: &str) -> i32 {
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if primary.is_empty() || pattern.is_empty() || primary.len() < pattern.len() { return -1; }
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let primary_chars: Vec<char> = primary.chars().collect();
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let pattern_chars: Vec<char> = pattern.chars().collect();
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for i in 0..(primary.len() - pattern.len() + 1) {
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if pattern_chars == primary_chars[i..i + pattern.len()].to_vec() {
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return i as i32;
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}
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}
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-1
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}
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// 通过哈希算法对主串中的 n-m+1 个子串分别求哈希值，
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// 逐个与模式串的哈希值比较大小。如果某个子串的哈希值与模式串相等，那就说明对应的子串和模式串匹配
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fn rk(primary: &str, pattern: &str) -> i32 {
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if primary.is_empty() || pattern.is_empty() || primary.len() < pattern.len() { return -1; }
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let primary_chars: Vec<char> = primary.chars().collect();
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let pattern_chars: Vec<char> = pattern.chars().collect();
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let base: i128 = 26;
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let m = pattern.len();
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let n = primary.len();
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let mut pow_vec = vec![];
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let mut hash = HashMap::new();
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// 存储 26 的 n 次方到数组中，方便后面调用
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for i in 0..m {
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pow_vec.push(base.pow(i as u32));
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}
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// 计算子串的 hash 值
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let mut p_value = 0;
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for i in 0..m {
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p_value += (pattern_chars[i] as i128 - 'a' as i128) * pow_vec[m-1-i];
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}
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// 计算主串的 n-m+1 个子串的 hash 值
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for i in 0..(n - m + 1) {
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// 计算主串中 index 为 0 的子串的 hash 值
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let mut value = 0;
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if i == 0 {
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for i in 0..m {
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value += (primary_chars[i] as i128 - 'a' as i128) * pow_vec[m-1-i];
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}
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} else {
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// 计算 index 为 i 的子串的 hash 值
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// 计算公式: hash[i] = (hash[i-1] - 26^(m-1) * (primary_chars[i-1] - 'a')) * 26 + (26^0 * (primary_chars[i+m-1] - 'a'))
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value = (hash[&((i-1) as i32)] - base.pow((m-1) as u32) * (primary_chars[i-1] as i128 - 'a' as i128)) * base + ((primary_chars[i+m-1]) as i128 - 'a' as i128);
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}
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// hash 值相等，比较两个串内容是否相等，避免 hash 碰撞
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if value == p_value && pattern_chars == primary_chars[i..i+m].to_vec() {
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return i as i32;
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}
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hash.insert(i as i32, value);
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}
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-1
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}
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fn main() {
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let primary = "thequickbrownfoxjumpsoverthelazydog";
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let pattern = "jump";
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let result = bf(primary, pattern);
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println!("{}", result); // 16
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let result2 = rk(primary, pattern);
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println!("{:?}", result2); // 16
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}
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