From b3956c9e88a7611705c57cee913dadd727e0cd66 Mon Sep 17 00:00:00 2001
From: krahets <krahets@163.com>
Date: Wed, 4 Oct 2023 02:44:58 +0800
Subject: [PATCH] build

---
 chapter_hashing/hash_algorithm.md |  1 +
 chapter_hashing/hash_collision.md | 10 +++++-----
 chapter_hashing/hash_map.md       |  2 +-
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/chapter_hashing/hash_algorithm.md b/chapter_hashing/hash_algorithm.md
index 4262878ba..927ae76f3 100644
--- a/chapter_hashing/hash_algorithm.md
+++ b/chapter_hashing/hash_algorithm.md
@@ -37,6 +37,7 @@ index = hash(key) % capacity
 
 对于密码学的相关应用，为了防止从哈希值推导出原始密码等逆向工程，哈希算法需要具备更高等级的安全特性。
 
+- **单向性**：无法通过哈希值反推出关于输入数据的任何信息。
 - **抗碰撞性**：应当极其困难找到两个不同的输入，使得它们的哈希值相同。
 - **雪崩效应**：输入的微小变化应当导致输出的显著且不可预测的变化。
 
diff --git a/chapter_hashing/hash_collision.md b/chapter_hashing/hash_collision.md
index 68cc3566b..a375d0284 100644
--- a/chapter_hashing/hash_collision.md
+++ b/chapter_hashing/hash_collision.md
@@ -59,7 +59,7 @@ comments: true
             """负载因子"""
             return self.size / self.capacity
 
-        def get(self, key: int) -> str:
+        def get(self, key: int) -> str | None:
             """查询操作"""
             index = self.hash_func(key)
             bucket = self.buckets[index]
@@ -167,8 +167,8 @@ comments: true
                     return pair->val;
                 }
             }
-            // 若未找到 key 则返回 nullptr
-            return nullptr;
+            // 若未找到 key 则返回空字符串
+            return "";
         }
 
         /* 添加操作 */
@@ -386,7 +386,7 @@ comments: true
         }
 
         /* 查询操作 */
-        public string get(int key) {
+        public string? get(int key) {
             int index = hashFunc(key);
             // 遍历桶，若找到 key 则返回对应 val
             foreach (Pair pair in buckets[index]) {
@@ -1792,7 +1792,7 @@ comments: true
         }
 
         /* 查询操作 */
-        public string get(int key) {
+        public string? get(int key) {
             // 搜索 key 对应的桶索引
             int index = findBucket(key);
             // 若找到键值对，则返回对应 val
diff --git a/chapter_hashing/hash_map.md b/chapter_hashing/hash_map.md
index 362c64211..8e09e6724 100755
--- a/chapter_hashing/hash_map.md
+++ b/chapter_hashing/hash_map.md
@@ -621,7 +621,7 @@ index = hash(key) % capacity
             int index = hashFunc(key);
             Pair *pair = buckets[index];
             if (pair == nullptr)
-                return nullptr;
+                return "";
             return pair->val;
         }