feat: update solutions to lcof problems: 04,50

- 面试题04. 二维数组中的查找
- 面试题50. 第一个只出现一次的字符

Author: YangFong

lcof/面试题04. 二维数组中的查找/README.md

@@ -188,27 +188,19 @@ function findNumberIn2DArray(matrix: number[][], target: number): boolean {
 ### **Rust**
 
 ```rust
+use std::cmp::Ordering;
 impl Solution {
     pub fn find_number_in2_d_array(matrix: Vec<Vec<i32>>, target: i32) -> bool {
-        let len_y = matrix.len();
-        if len_y == 0 {
+        if matrix.len() == 0 || matrix[0].len() == 0 {
             return false;
         }
-        let len_x = matrix[0].len();
-        if len_x == 0 {
-            return false;
-        }
-
-        let mut x = len_x - 1;
-        let mut y = 0;
-        while y < len_y {
-            match target.cmp(&matrix[y][x]) {
-                std::cmp::Ordering::Greater => y += 1,
-                std::cmp::Ordering::Equal => return true,
-                std::cmp::Ordering::Less => match x {
-                    0 => return false,
-                    _ => x -= 1,
-                },
+        let (m, n) = (matrix.len(), matrix[0].len());
+        let (mut i, mut j) = (0, n);
+        while i < m && j > 0 {
+            match target.cmp(&matrix[i][j - 1]) {
+                Ordering::Less => j -= 1,
+                Ordering::Greater => i += 1,
+                Ordering::Equal => return true,
             }
         }
         false

lcof/面试题04. 二维数组中的查找/Solution.rs

@@ -1,24 +1,16 @@
+use std::cmp::Ordering;
 impl Solution {
     pub fn find_number_in2_d_array(matrix: Vec<Vec<i32>>, target: i32) -> bool {
-        let len_y = matrix.len();
-        if len_y == 0 {
+        if matrix.len() == 0 || matrix[0].len() == 0 {
             return false;
         }
-        let len_x = matrix[0].len();
-        if len_x == 0 {
-            return false;
-        }
-
-        let mut x = len_x - 1;
-        let mut y = 0;
-        while y < len_y {
-            match target.cmp(&matrix[y][x]) {
-                std::cmp::Ordering::Greater => y += 1,
-                std::cmp::Ordering::Equal => return true,
-                std::cmp::Ordering::Less => match x {
-                    0 => return false,
-                    _ => x -= 1,
-                },
+        let (m, n) = (matrix.len(), matrix[0].len());
+        let (mut i, mut j) = (0, n);
+        while i < m && j > 0 {
+            match target.cmp(&matrix[i][j - 1]) {
+                Ordering::Less => j -= 1,
+                Ordering::Greater => i += 1,
+                Ordering::Equal => return true,
             }
         }
         false

lcof/面试题50. 第一个只出现一次的字符/README.md

@@ -28,9 +28,9 @@
 
 对字符串进行两次遍历：
 
-第一遍，先用 hash 表（或数组）统计字符串中每个字符出现的次数。
+第一遍，使用 hash 表（或数组）统计字符串中每个字符出现的次数。
 
-第二遍，只要遍历到一个只出现一次的字符，那么就返回该字符，否则在遍历结束后返回空格。
+第二遍，只要遍历到一个只出现一次的字符，那么就返回该字符，否则在遍历结束后，返回 `' '`。
 
 <!-- tabs:start -->
 
@@ -130,22 +130,15 @@ function firstUniqChar(s: string): string {
 
 ```rust
 use std::collections::HashMap;
-
 impl Solution {
     pub fn first_uniq_char(s: String) -> char {
         let mut map = HashMap::new();
-        let s = s.chars().collect::<Vec<char>>();
-        for c in s.iter() {
-            match map.contains_key(c) {
-                true => map.insert(c, false),
-                false => map.insert(c, true),
-            };
+        for c in s.as_bytes() {
+            map.insert(c, !map.contains_key(c));
         }
-        for c in s.iter() {
-            if let Some(is_single) = map.get(c) {
-                if *is_single {
-                    return *c;
-                }
+        for c in s.as_bytes() {
+            if map[c] {
+                return char::from(*c);
             }
         }
         ' '

lcof/面试题50. 第一个只出现一次的字符/Solution.rs

@@ -1,20 +1,13 @@
 use std::collections::HashMap;
-
 impl Solution {
     pub fn first_uniq_char(s: String) -> char {
         let mut map = HashMap::new();
-        let s = s.chars().collect::<Vec<char>>();
-        for c in s.iter() {
-            match map.contains_key(c) {
-                true => map.insert(c, false),
-                false => map.insert(c, true),
-            };
+        for c in s.as_bytes() {
+            map.insert(c, !map.contains_key(c));
         }
-        for c in s.iter() {
-            if let Some(is_single) = map.get(c) {
-                if *is_single {
-                    return *c;
-                }
+        for c in s.as_bytes() {
+            if map[c] {
+                return char::from(*c);
             }
         }
         ' '