leetcode: Add 0389

src/leetcode/0389.find-the-difference/Cargo.toml

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+[package]
+name = "lc-0389-find-the-difference"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+[dependencies]

src/leetcode/0389.find-the-difference/index.md

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+
+# 
+
+[问题描述](../problems/)

src/leetcode/0389.find-the-difference/src/main.rs

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+// 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.
+
+// 排序
+pub fn find_the_difference1(s: String, t: String) -> char {
+    debug_assert!(s.len() + 1 == t.len());
+
+    // 先排序
+    let mut s_chars: Vec<char> = s.chars().collect();
+    s_chars.sort_unstable();
+    let mut t_chars: Vec<char> = t.chars().collect();
+    t_chars.sort_unstable();
+
+    // TODO(Shaohua): binary search
+
+    // 再依次遍历
+    for (s_chr, t_chr) in s_chars.iter().zip(t_chars.iter()) {
+        if s_chr != t_chr {
+            return *t_chr;
+        }
+    }
+
+    t_chars.last().copied().unwrap()
+}
+
+// 转换成整数, 求和
+pub fn find_the_difference2(s: String, t: String) -> char {
+    let sum_s: u32 = s.chars().map(|chr| chr as u32).sum();
+    let sum_t: u32 = t.chars().map(|chr| chr as u32).sum();
+    char::from_u32(sum_t - sum_s).unwrap()
+}
+
+pub type SolutionFn = fn(String, String) -> char;
+
+fn check_solution(func: SolutionFn) {
+    let s = "abcd".to_owned();
+    let t = "abcde".to_owned();
+    assert_eq!(func(s, t), 'e');
+
+    let s = "".to_owned();
+    let t = "y".to_owned();
+    assert_eq!(func(s, t), 'y');
+}
+
+fn main() {
+    check_solution(find_the_difference1);
+    check_solution(find_the_difference2);
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{check_solution, find_the_difference1, find_the_difference2};
+
+    #[test]
+    fn test_find_the_difference1() {
+        check_solution(find_the_difference1);
+    }
+
+    #[test]
+    fn test_find_the_difference2() {
+        check_solution(find_the_difference2);
+    }
+}