在構建好二叉樹後，需要通過一次遍歷來給每個結點的parent賦值,關鍵程式碼如下:

void triBtee(BTNode *p,BTNode *q)//給各個結點的parent賦值
{
	if(p == nullptr)
		return;
	p->parent = q;
	q = p;
	triBtee(p->left,q);
	triBtee(p->right,q);
}

void printPath(BTNode *p){
	while(p != nullptr){
		cout<<p->value<<" ";
		p = p->parent;
	}
}

void allPath(BTNode *p){
	if(p == nullptr)
		return;
	printPath(p);
	cout<<endl;
	allPath(p->left);
	allPath(p->right);
}
 

完整程式碼如下:

#include<iostream>
#include<algorithm>
using namespace std;
 
typedef struct BTNode{
	int value;
	BTNode *parent;
	BTNode *left;
	BTNode *right;
}BTNode;

 
void addBTNode(BTNode *&myBT,int val);
void createBT(BTNode *&BT,int arr[],int n);

void triBtee(BTNode *p,BTNode *q);//給各個結點的parent賦值,p當前結點,q父結點
void printPath(BTNode *p);
void allPath(BTNode *p);
 
int main(){
	BTNode *myBT = nullptr;
	int arr[] = {314,426,12,78,143,8,21,14,9};
	createBT(myBT,arr,sizeof(arr)/sizeof(arr[0]));
	
	triBtee(myBT,nullptr);
	allPath(myBT);
	
	return 0;
}

void triBtee(BTNode *p,BTNode *q)//給各個結點的parent賦值
{
	if(p == nullptr)
		return;
	p->parent = q;
	q = p;
	triBtee(p->left,q);
	triBtee(p->right,q);
}

void printPath(BTNode *p){
	while(p != nullptr){
		cout<<p->value<<" ";
		p = p->parent;
	}
}

void allPath(BTNode *p){
	if(p == nullptr)
		return;
	printPath(p);
	cout<<endl;
	allPath(p->left);
	allPath(p->right);
}


void createBT(BTNode *&BT,int arr[],int n){
	BT = nullptr;
	for(int i=0;i<n;i++)
		addBTNode(BT,arr[i]);	
}

void addBTNode(BTNode *&myBT,int val){
	if(myBT == nullptr){
		myBT = new BTNode();
		myBT->value = val;
		myBT->left = myBT->right = nullptr;
		return;	
	}
		
	if(val == myBT->value){
		return;
	}
	else if(val < myBT->value){
		addBTNode(myBT->left,val);
	}
	else{
		addBTNode(myBT->right,val);
	}			
}
 
 

執行結果如下: