%%{init: {'flowchart': {'nodeSpacing': 15, 'rankSpacing': 25, 'padding': 20}}}%%
graph LR
    S(["开始"]) --> INPUT["输入根节点"]
    INPUT --> TYPE{"遍历类型?"}
    TYPE -->|"前序DFS"| PRE["访问节点 → 左子树 → 右子树"]
    TYPE -->|"中序DFS"| IN["左子树 → 访问节点 → 右子树"]
    TYPE -->|"后序DFS"| POST["左子树 → 右子树 → 访问节点"]
    TYPE -->|"BFS"| BFS["队列实现逐层访问"]
    TYPE -->|"Morris"| MORRIS["O1空间遍历"]
    PRE --> CHECK1{"节点为空?"}
    IN --> CHECK1
    POST --> CHECK1
    BFS --> CHECK2{"队列为空?"}
    MORRIS --> CHECK3{"当前节点为空?"}
    CHECK1 -->|"是"| END(["结束"])
    CHECK1 -->|"否"| RECURSE["递归处理"]
    CHECK2 -->|"是"| END
    CHECK2 -->|"否"| DEQUEUE["出队并访问"]
    CHECK3 -->|"是"| END
    CHECK3 -->|"否"| LEFTMORRIS{"有左子树?"}
    DEQUEUE --> CHILD["入队子节点"]
    CHILD --> CHECK2
    RECURSE --> END
    LEFTMORRIS -->|"是"| PREDECESSOR["找到前驱节点"]
    LEFTMORRIS -->|"否"| VISIT["访问当前节点"]
    PREDECESSOR --> THREAD{"前驱右指针为空?"}
    THREAD -->|"是"| SETTHREAD["设置线索指向当前节点"]
    THREAD -->|"否"| RESTORE["恢复树结构"]
    SETTHREAD --> LEFT["当前节点=左子树"]
    RESTORE --> VISIT
    VISIT --> RIGHT["当前节点=右子树"]
    LEFT --> CHECK3
    RIGHT --> CHECK3

    %% 节点样式
    classDef start fill:#ff7f50,color:#fff,stroke:#e5533c,stroke-width:2px
    classDef end1 fill:#ff7f50,color:#fff,stroke:#e5533c,stroke-width:2px
    classDef decision fill:#6a5acd,color:#fff,stroke:#483d8b,stroke-width:2px
    classDef process fill:#20b2aa,color:#fff,stroke:#008080,stroke-width:2px
    
    %% 应用样式
    class S,END start
    class TYPE,CHECK1,CHECK2,CHECK3,THREAD,LEFTMORRIS decision
    class INPUT,PRE,IN,POST,BFS,MORRIS,RECURSE,DEQUEUE,CHILD,PREDECESSOR,SETTHREAD,RESTORE,VISIT,LEFT,RIGHT process