求最近公共祖先和所有祖先

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/LYJ_viviani/article/details/67632565

#include "btree.cpp" //二叉链的基本运算
#include<iostream>

using namespace std;

bool allAncestor(BTNode *b, ElemType t)//求所有祖先节点
{
    if (b == NULL)
        return false;
    else if ((b->lchild != NULL && b->lchild->data == t) || (b->rchild != NULL && b->rchild->data == t))
    {
        cout<< b->data<<" ";
        return true;
    }
    else if (allAncestor(b->lchild, t) || allAncestor(b->rchild, t))
    {
        cout<< b->data<<" ";
        return true;    
    }
    else 
        return false;
}

BTNode *nearestAncestor(BTNode *b,ElemType x,ElemType y)//求x和y的最近公共祖先
{
    if(b==NULL || b->data==x || b->data==y)
        return b;
    BTNode *left=nearestAncestor(b->lchild,x,y);
    BTNode *right=nearestAncestor(b->rchild,x,y);
    if(left!=NULL && right!=NULL)
        return b;
    else if(left!=NULL)
        return left;//等价于left!=NULL && right==NULL
    else
        return right;//等价于left==NULL && right!=NULL或者left==NULL && right==NULL
}

int main()
{
    BTNode *b;
    ElemType x = 'F', y = 'H';
    CreateBTNode(b,"A(B(D,E),C(F,G(,H)))");
    cout<<"二叉树b为:";DispBTNode(b);cout<<endl;
    cout<<"结点"<<x<<"和"<<y<<"的最近公共祖先为:"<<nearestAncestor(b,x,y)->data<<endl;
    cout<<"结点"<<y<<"的所有祖先为:";allAncestor(b, y);cout<<endl;
    return 0;
}

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