트리 순회 (전위 순회, 중위 순회, 후위 순회)

#include <iostream>
using namespace std;

char tree[26][2];  // 각 노드의 왼쪽/오른쪽 자식 저장

void preorder(char node) {
    if (node == '.') return;
    cout << node;
    preorder(tree[node - 'A'][0]);
    preorder(tree[node - 'A'][1]);
}

void inorder(char node) {
    if (node == '.') return;
    inorder(tree[node - 'A'][0]);
    cout << node;
    inorder(tree[node - 'A'][1]);
}

void postorder(char node) {
    if (node == '.') return;
    postorder(tree[node - 'A'][0]);
    postorder(tree[node - 'A'][1]);
    cout << node;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int N;
    cin >> N;
    for (int i = 0; i < N; i++) {
        char parent, left, right;
        cin >> parent >> left >> right;
        tree[parent - 'A'][0] = left;
        tree[parent - 'A'][1] = right;
    }

    preorder('A'); cout << "\n";
    inorder('A'); cout << "\n";
    postorder('A'); cout << "\n";

    return 0;
}