1991 트리 순회

#include <stdio.h>
#include <vector>
#include <utility>
 
using namespace std;
 
vector<pair<int, int> > arr(30);
 
int ctoi(char c) {
    return (int)(c - 'A' + 1);
}
 
char itoc(int n) {
    return (char)(n + 'A' - 1);
}
 
void preorder(int c);
void inorder(int c);
void postorder(int c);
 
int main() {
    int n;
    scanf("%d", &n);
    getchar();
    int t = n;
 
    while (n--) {
        char a, b, c;
        int idx1 = 0, idx2 = 0, idx3 = 0;
        scanf("%c %c %c", &a, &b, &c);
        getchar();
 
        if ('A' <= a && a <= 'Z')
            idx1 = ctoi(a);
        if ('A' <= b && b <= 'Z') 
            idx2 = ctoi(b);        
        if ('A' <= c && c <= 'Z')
            idx3 = ctoi(c);
        
        arr[idx1].first = idx2;
        arr[idx1].second = idx3;            
    }
 
    preorder(1);
    printf("\n");
 
    inorder(1);
    printf("\n");
 
    postorder(1);
    printf("\n");
}
 
void preorder(int n) {
    if (n == 0)
        return;
 
    char alpha = itoc(n);
    printf("%c", alpha);
 
    preorder(arr[n].first);
    preorder(arr[n].second);    
}
 
void inorder(int n) {
    if (n == 0)
        return;
 
    inorder(arr[n].first);
 
    char alpha = itoc(n);
    printf("%c", alpha);
    
    inorder(arr[n].second);
}
 
void postorder(int n) {
    if (n == 0)
        return;
 
    postorder(arr[n].first);
    postorder(arr[n].second);
 
    char alpha = itoc(n);
    printf("%c", alpha);    
}