트리 순회(1991).cc

#include<stdio.h>
#include<stdlib.h>
#define node_num 26

//node struct
typedef struct node
{
	char alphabet;  //alphabet
	struct node* left; //left child node
	struct node* right; //right child node
}node;

//set up information of node
void set_node(node* n, char alphabet, node* left, node* right)
{
	n->alphabet = alphabet;
	n->left = left;
	n->right = right;
}

//preorder
void preorder(node* root)
{
	printf("%c", root->alphabet); //print node
	if(root->left) preorder(root->left); //left child
	if (root->right) preorder(root->right); //right child
}

//inorder
void inorder(node* root)
{
	if (root->left) inorder(root->left); //left child
	printf("%c", root->alphabet); //print node
	if (root->right) inorder(root->right); //right child
}

//postorder
void postorder(node* root)
{
	if (root->left) postorder(root->left); //left child
	if (root->right) postorder(root->right); //right child
	printf("%c", root->alphabet); //print node
}

int main()
{
	int i, num;
	char me, left, right;
	node* arr_node[node_num];
	scanf("%d", &num);

	for (i = 0; i < num; i++)
		arr_node[i] = (node*)malloc(sizeof(node));

	for (i = 0; i < num; i++)
	{
		//arr_node[i] = (node*)malloc(sizeof(node));
		getchar();
		scanf("%c %c %c", &me, &left, &right);
		if (left == '.')
		{
			if(right=='.')
				set_node(arr_node[me-'A'], me, NULL, NULL);
			else
				set_node(arr_node[me - 'A'], me, NULL, arr_node[right-'A']);
		}
		else if (right == '.')
			set_node(arr_node[me - 'A'], me, arr_node[left-'A'], NULL);
		else
			set_node(arr_node[me - 'A'], me, arr_node[left-'A'], arr_node[right-'A']);
	}
	
	preorder(arr_node[0]); printf("\n");
	inorder(arr_node[0]); printf("\n");
	postorder(arr_node[0]); printf("\n");
	
	return 0;
}