e100: Add rust impl of length of continous letters

src/od/2024e100/length-of-continous-letters/index.md

@@ -86,4 +86,10 @@
 
 ```python
 {{#include solution.py:6:}}
+```
+
+### Rust
+
+```rust
+{{#include src/main.rs:5:}}
 ```

src/od/2024e100/length-of-continous-letters/src/main.rs

@@ -1,3 +1,66 @@
+// Copyright (c) 2024 Xu Shaohua <[email protected]>. All rights reserved.
+// Use of this source is governed by General Public License that can be found
+// in the LICENSE file.
+
+use std::cmp::Reverse;
+use std::collections::HashMap;
+use std::io::{stdin, BufRead};
+
 fn main() {
-    println!("Hello, world!");
+    // 读取输入
+    let mut s = String::new();
+    let ret = stdin().lock().read_line(&mut s);
+    assert!(ret.is_ok());
+    let mut k_str = String::new();
+    let ret = stdin().lock().read_line(&mut k_str);
+    assert!(ret.is_ok());
+    let k: usize = k_str.trim().parse().unwrap();
+
+    // 先遍历字符串, 分隔出连续相同字符, 然后统计其个数, 存放到计数字典中
+    let mut current_char: char = 'A';
+    let mut current_char_count: usize = 0;
+    let mut char_dict: HashMap<char, usize> = HashMap::new();
+    for chr in s.trim().chars() {
+        // 如果当前的字符与上个字符不相同
+        if current_char != chr {
+            // 保存到字典中
+            if current_char_count > 0 {
+                // 如果该字符在字典中已经存在, 则只保存最大连续数
+                if let Some(last_count) = char_dict.get_mut(&current_char) {
+                    *last_count = current_char_count.max(*last_count);
+                } else {
+                    char_dict.insert(current_char, current_char_count);
+                }
+            }
+
+            // 重置上个字符及其计数
+            current_char = chr;
+            current_char_count = 1;
+        } else {
+            current_char_count += 1;
+        }
+    }
+
+    // 处理最后一个字符
+    if current_char_count > 0 {
+        // 如果该字符在字典中已经存在, 则只保存最大连续数
+        if let Some(last_count) = char_dict.get_mut(&current_char) {
+            *last_count = current_char_count.max(*last_count);
+        } else {
+            char_dict.insert(current_char, current_char_count);
+        }
+    }
+
+    // 将字典转换成列表
+    let mut word_list: Vec<(char, usize)> = char_dict.into_iter().collect();
+    // 基于最大连续数进行排序, 从高到低
+    word_list.sort_by_key(|pair| Reverse(pair.1));
+    //println!("{word_list:?}");
+
+    // 并找到第 k 个字符, 注意下标从0开始计数, 而k是从1开始的
+    if k <= word_list.len() {
+        println!("{}", word_list[k - 1].1);
+    } else {
+        println!("-1");
+    }
 }