一般树->二叉树->打印（数据结构）

Question

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#pragma warning(disable: 4996)

typedef struct node {
    int level;
    int key;
    int child_key;
    struct node* left;
    struct node* right;
} Node;

Node* root = NULL;

// function to create a new node
Node* newNode(int level, int key, int child_key) {
    Node* node = (Node*)malloc(sizeof(Node));
    node->level = level;
    node->key = key;
    node->child_key = child_key;
    node->left = NULL;
    node->right = NULL;
    return node;
}

// read the general tree input
void input(Node* node, int level, int key, int child_key) {
    if (node->level == level) {
        if (node->right == NULL) {
            node->right = newNode(level, key, child_key);
            return;
        }
        else 
            input(node->right, level, key, child_key);
    }
    else {
        if (node->child_key == key) {
            node->left = newNode(level, key, child_key);
            return;
        }
        else {
            if (root->left == NULL)
                input(node->right, level, key, child_key);
            else
                input(node->left, level, key, child_key);
        }
    }
}

// function to traverse a binary tree in preorder and print the keys of the nodes visited
void traversePreorder(Node* root) {
    if (root != NULL) {
        printf("%d ", root->key);
        traversePreorder(root->left);
        traversePreorder(root->right);
    }
}

int main() {
    int level, key, child_key;
    char child[5];

    while (1) {
        printf("Please input data following format\n");
        printf("(if you want to stop, input = 0 0 0)\n");
        printf("(tree-level, key, child_key) -> 1 100 75 : ");
        scanf("%d %d %s", &level, &key, child);
     
        if (level == 0)
            break;

        if (strcmp(child ,"NULL\n")==0)
            child_key = 0;
        else 
            child_key = atoi(child);

        if (level == 1) {
            root = newNode(level, key, child_key);
        }
        else
            input(root, level, key, child_key);
        printf("\n");
    }
    printf("[Preorder traversal result]\n");
    traversePreorder(root);

    return 0;
}

你知道为什么当我输入 (3 25 NULL) 时程序会退出吗？

这是我的任务。所以，我花了很多时间来解决这个问题，但我做不到。

输入： (1 100 200) (2 200 NULL) (2 75 25) (2 300 NULL) (3 25 NULL) (3 50 NULL) (3 30 120) (3 150 NULL) (4 120 NULL) (4 55 NULL)

输出：100 200 75 300 25 50 30 120 55 150

Answer 1

我认为你的意思是

node

而不是

root

在

input()

：

void input(Node* node, int level, int key, int child_key) {
    if (node->level == level)
        if (node->right)
            input(node->right, level, key, child_key);
        else
            node->right = newNode(level, key, child_key);
    else
        if (node->child_key == key)
            node->left = newNode(level, key, child_key);
        else
            if (node->left)
                input(node->left, level, key, child_key);
            else
                input(node->right, level, key, child_key);
}

和示例运行（注意这不是预期的输出，但它不再崩溃）：

$ echo -e "1 100 200\n2 200 NULL\n2 75 25\n2 300 NULL\n3 25 NULL\n3 50 NULL\n3 30 120\n3 150 NULL\n4 120 NULL\n4 55 NULL\n0 0 0" | ./a.out
100 200 75 25 50 30 120 55 150 300