백준 1991번 C++ 풀이

#include <iostream>
#include <algorithm>
#include <queue>
using namespace std;
struct node {
    int value;
    node * left;
    node * right;
};
struct node  tree[28];

void preFix(node a){
    cout << (char) (a.value+'A');
    if (a.left != NULL){
        preFix(*a.left);
    }
    if (a.right != NULL){
        preFix(*a.right);
    }
}
void inOrder(node a){
    if (a.left != NULL){
        inOrder(*a.left);
    }
    cout << (char) (a.value+'A');

    if (a.right != NULL){
        inOrder(*a.right);
    }
}
void postFix(node a){
    if (a.left != NULL){
        postFix(*a.left);
    }
    if (a.right != NULL){
        postFix(*a.right);
    }

    cout << (char) (a.value+'A');

 }

int main() {
    cin.tie(NULL);
    ios::sync_with_stdio(false);
    int n;
    cin >> n;
    for (auto i=0; i<n; i++){
        tree[i].value = i;
    }
    for (auto i=0; i<n; i++){
        char value, left, right;
        cin >> value >> left >> right;
//        cout << value- 'A';
        if (left != '.'){
            tree[value- 'A'].left = &tree[ (left-'A')];
        }
        if (right != '.'){
            tree[value- 'A'].right = &tree[ (right-'A')];
        }
    }
    preFix(tree[0]);
    cout << '\n';
    inOrder(tree[0]);
    cout << '\n';
    postFix(tree[0]);

}