C二进制搜索树没有为左右节点赋值

Question

我似乎遇到了一个问题，当我将值分配到二进制搜索树时，根将接收输入的第一个值，但之后就不输入其他值了。如果我直接查看root->left或root->right，它只返回null。我盯着这个看了太久了，简直不知所措。我确信我的递归确实有一些基本的错误，但我就是看不出来。我真的很感激任何帮助，看看我在哪里出错了。

#include <stdio.h>
#include <stdlib.h>
#include "Bst.h"

int main(int argc, char** argv) {
    int value;
    TreeNode* root = NULL;
    printf ("Enter an integern");
    scanf ("%d", &value);
    while (value > 0) {
        root = insert (value, root);
        printf ("Enter an integern");
        scanf ("%d", &value);    
    }
    printf("The inorder traversal of the treen");
    inOrder(root);
    printf("n");
    printf("The preorder traversal of the treen");
    preOrder(root);
    printf("n");
    return (EXIT_SUCCESS);
}

TreeNode* insert(int newValue, TreeNode* root) {
    TreeNode* temp = NULL;
    //Sets a value to the root
    if (root == NULL) {
        temp = (TreeNode*)malloc(sizeof(TreeNode));
        temp -> value = newValue;
        temp -> left = NULL;
        temp -> right = NULL;
        return temp;
    }
    //Will put a larger value to the right within the tree
    else if (newValue > (root -> value)) {
        temp = insert(newValue, (root -> right));
    }
    //Will put a smaller value to the left
    else {
        temp = insert (newValue, (root -> left));
    }
    return root;
}
void inOrder(TreeNode* root){
    if(root == NULL){
        return;
    }
    else {
        inOrder(root -> left);
        printf("%d", root -> value);
        printf(" ");
        inOrder(root -> right);
    }
    return;
}
void preOrder(TreeNode* root){
    if(root == NULL) {
        return;
    } else {
        preOrder(root -> right);
        printf("%d", root -> value);
        printf(" ");
        preOrder(root -> left);
    }
    return;
}

Answer 1

更改：

temp = insert(newValue, (root -> right));

至

root->right = insert(newValue, (root -> right));

也以相同的方式更改左侧版本。现在您正在分配子节点，但从未将它们分配给右指针或左指针。他们基本上被抛弃了。

Answer 2

可以肯定的是，错误是将新插入的右节点和左节点分配给temp，而不是root->right和root->left，这会使它们在树外悬空。

更改这些行：

//Will put a larger value to the right within the tree
else if (newValue > (root -> value)){
    temp = insert(newValue, (root -> right));
}
//Will put a smaller value to the left
else{
    temp = insert (newValue, (root -> left));
}

对此：

//Will put a larger value to the right within the tree
    else if (newValue > (root -> value)) {
        root->right = insert(newValue, (root -> right));
    }
//Will put a smaller value to the left
    else {
        root->left = insert (newValue, (root -> left));
    }

此更改使您的代码在我测试时能够按预期工作；inOrder和preOrder都给出了正确的结果。

请参阅此Ideone示例