chore: initialize repository with gitignore

hw2/diagrams/cause-effect.puml

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+@startuml cause-effect
+title 因果图 — 登录功能输入验证
+
+' ========== 布局 ==========
+left to right direction
+skinparam defaultTextAlignment center
+skinparam rectangle {
+    RoundCorner 15
+}
+
+' ========== 原因 (Causes) ==========
+rectangle "原因" as causes {
+    rectangle "C1\n账号长度 ≥ 6" as C1 #LightBlue
+    rectangle "C2\n账号长度 ≤ 10" as C2 #LightBlue
+    rectangle "C3\n账号为纯数字\n（自然数）" as C3 #LightBlue
+    rectangle "C4\n密码长度 = 8" as C4 #LightBlue
+}
+
+' ========== 中间节点 ==========
+rectangle "M1\n账号合法\n(C1 ∧ C2 ∧ C3)" as M1 #Wheat
+
+' ========== 结果 (Effects) ==========
+rectangle "结果" as effects {
+    rectangle "E1\n显示\"输入合法\"" as E1 #LightGreen
+    rectangle "E2\n显示\"账号不合法\"" as E2 #Salmon
+    rectangle "E3\n显示\"密码不合法\"" as E3 #Salmon
+}
+
+' ========== 关系 ==========
+C1 --> M1 : AND
+C2 --> M1 : AND
+C3 --> M1 : AND
+
+M1 --> E1 : AND
+C4 --> E1 : AND
+
+M1 ..> E2 : NOT\n(~M1 → E2)
+C4 ..> E3 : NOT\n(~C4 → E3)
+
+' ========== 约束 ==========
+note bottom of causes
+  约束: C1, C2, C3 相互独立
+  C4 独立于 C1/C2/C3
+end note
+
+@enduml

hw2/diagrams/decision-table.puml

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+@startsalt
+title 判定表 — 登录功能输入验证
+{+
+<style>
+header {
+  FontStyle bold
+}
+</style>
+{#
+**条件/动作** | **R1** | **R2** | **R3** | **R4** | **R5** | **R6** | **R7** | **R8**
+. | . | . | . | . | . | . | . | .
+**C1: 账号长度>=6** | T | T | T | T | F | F | F | F
+**C2: 账号长度<=10** | T | T | F | F | - | - | - | -
+**C3: 账号为纯数字** | T | T | - | - | - | - | - | -
+**C4: 密码长度=8** | T | F | T | F | T | F | T | F
+. | . | . | . | . | . | . | . | .
+**E1: 输入合法** | V |   |   |   |   |   |   |  
+**E2: 账号不合法** |   |   | V | V | V | V | V | V
+**E3: 密码不合法** |   | V |   | V |   | V |   | V
+}
+--
+{
+T = 条件为真, F = 条件为假, "-" = 不影响结果
+V = 触发该动作
+..
+**简化后 4 条规则:**
+{#
+**规则** | **账号合法** | **密码合法** | **结果**
+R1 | T | T | 输入合法
+R2 | T | F | 密码不合法
+R3 | F | T | 账号不合法
+R4 | F | F | 账号不合法 + 密码不合法
+}
+}
+}
+@endsalt