根据已知节点求父节点（C语言，二叉树）

#include<stdio.h>
#include<stdlib.h>
struct TreeNode{
    int data;
    struct TreeNode *left;
    struct TreeNode *right;
};
struct TreeNode *createNode(int num){
    struct TreeNode *T;
    T=(struct TreeNode *)malloc(sizeof(struct TreeNode));
    T->left=NULL;
    T->right=NULL;
    T->data=num;
    return T;
}
struct TreeNode *createTree(struct TreeNode *T,int num){
    if(T==NULL){
        return createNode(num);
    }
    if(T->data>num){
        T->left=createTree(T->left,num);
    }else if(T->data<num){
        T->right=createTree(T->right,num);
    }
    return T;
}
struct TreeNode *Parent(struct TreeNode *T,struct TreeNode *p){/*根据已知节点求父节点的核心代码*/
    if(T==NULL||T==p||p==NULL){/*T==p说明p是根节点，所有没有父节点*/
    	return NULL;
	}
	if(T->left==p||T->right==p){/*在递归过程中除根节点以外的所有节点总会先被这句代码检查一次，所以T==P只会在根节点处可能被成功触发*/
		return T;
	}
	struct TreeNode *temp;
	temp=Parent(T->left,p);
	if(temp!=NULL){
		return temp;
	}else{
		return Parent(T->right,p);
	}
}
void preOrder(struct TreeNode *T){
    if(T!=NULL){
        printf("\t%d",T->data);
        preOrder(T->left);
        preOrder(T->right);
    }
}
void inOrder(struct TreeNode *T){
    if(T!=NULL){
        inOrder(T->left);
        printf("\t%d",T->data);
        inOrder(T->right);
    }
}
void postOrder(struct TreeNode *T){
    if(T!=NULL){
        postOrder(T->left);
        postOrder(T->right);
        printf("\t%d",T->data);
    }
}
int main(){
    struct TreeNode *T,*re,*temp;
    T=NULL;
    for(int i=1;i<6;i++){
        T=createTree(T,i);    }
    printf("二叉树:\n前序遍历:");
    preOrder(T);
    printf("\n中序遍历:");
    inOrder(T);
    printf("\n后序遍历:");
    postOrder(T);
    temp=T->right->right->right->right;
    re=Parent(T,temp);
    printf("\n父节点值为:");
    if(re){
        printf("%d",re->data);
    }else{
        printf("NULL");
    }
    return 0;
}