C++ | 以漂亮的方式將樹（不一定是二進制）打印到標准輸出

Question

假設我有一個這樣的struct ：

    struct Node {
        int val = 0;
        std::vector<Node *> _children{};
    };

如何以整潔漂亮的方式將其打印到stdout ？ 例如像tree程序打印出目錄結構的方式。

parent/
├── child1
│   ├── cchild1
│   ├── cchild2
│   ├── child3
│   │   └── child1
│   └── child4
│       ├── child1
│       └── child2
└── child2
    └── cchild1
        └── ccchild1

它不必完全按照上面的格式，因為我在這里並沒有什么偏好。

這個問題與此不同，因為我想漂亮地打印一棵有多個孩子的樹。

Answer 1

通過修改此答案中的代碼，我設法使其適用於具有多個孩子的 Tree

void Node::printSubtree(const std::string &prefix) {
    using std::cout;
    using std::endl;
    if (_children.empty()) return;
    cout << prefix;
    size_t n_children = _children.size();
    cout << (n_children > 1 ? "├── " : "");

    for (size_t i = 0; i < n_children; ++i) {
        Node *c = _children[i];
        if (i < n_children - 1) {
            bool printStrand = n_children > 1 && !c->_children.empty();
            std::string newPrefix = prefix + (printStrand ? "│\t" : "\t");
            std::cout << val << "\n";
            c->printSubtree(newPrefix);
        } else {
            cout << (n_children > 1 ? prefix : "") << "└── ";
            std::cout << val << "\n";
            c->printSubtree(prefix + "\t");
        }
    }
}

void Node::printTree() {
    using std::cout;
    std::cout << val << "\n";
    printSubtree("");
    cout << "\n";
}

但是，歡迎新的解決方案。

Answer 2

要在 if (i < n_children - 1) 條件下修復縮進，並給出整個示例，這是我調整的代碼：

#include <iostream>
#include <vector>

using namespace std;

class Node {
 public:
    Node(std::string val) {
        this->val = val;
    }
    std::vector<Node*> _children;
    std::string val;
    void printSubtree(const std::string &prefix) {
        using std::cout;
        using std::endl;
        if (_children.empty()) return;
        cout << prefix;
        size_t n_children = _children.size();
        cout << (n_children > 1 ? "├── " : "");
    
        for (size_t i = 0; i < n_children; ++i) {
            Node *c = _children[i];
            if (i < n_children - 1) {
                if (i > 0) { // added fix
                    cout << prefix<< "├── "; // added fix
                } // added fix
                bool printStrand = n_children > 1 && !c->_children.empty();
                std::string newPrefix = prefix + (printStrand ? "│\t" : "\t");
                std::cout << c->val << "\n";
                c->printSubtree(newPrefix);
            } else {
                cout << (n_children > 1 ? prefix : "") << "└── ";
                std::cout << c->val << "\n";
                c->printSubtree(prefix + "\t");
            }
        }
    }
    
    void printTree() {
        using std::cout;
        std::cout << val << "\n";
        printSubtree("");
        cout << "\n";
    }
};

int main()
{
    Node root("root");
    Node node1("c1");
    Node node11("c11");
    Node node12("c12");
    Node node13("c13");
    node1._children.push_back(&node11);
    node1._children.push_back(&node12);
    node1._children.push_back(&node13);
    
    Node node111("c111");
    node11._children.push_back(&node111);
    Node node112("c112");
    node11._children.push_back(&node112);
    Node node113("c113");
    node11._children.push_back(&node113);
    Node node114("c114");
    node11._children.push_back(&node114);
    Node node115("c115");
    node11._children.push_back(&node115);
    Node node116("c116");
    node11._children.push_back(&node116);
    
    
    Node node2("c2");
    Node node21("c21");
    node2._children.push_back(&node21);
    Node node211("c211");
    node21._children.push_back(&node211);
    Node node2111("c2111");
    node211._children.push_back(&node2111);
    
    Node node3("c3");
    Node node31("c31");
    node3._children.push_back(&node31);
    Node node4("c4");

    root._children.push_back(&node1);
    root._children.push_back(&node2);
    root._children.push_back(&node3);
    root._children.push_back(&node4);

    root.printTree();
   
   return 0;
}

root
├── c1
│   ├── c11
│   │   ├── c111
│   │   ├── c112
│   │   ├── c113
│   │   ├── c114
│   │   ├── c115
│   │   └── c116
│   ├── c12
│   └── c13
├── c2
│   └── c21
│       └── c211
│           └── c2111
├── c3
│   └── c31
└── c4

我使用https://www.tutorialspoint.com/compile_cpp_online.php來測試它。