面试题50—树中两个节点的最低公共祖先

示例代码：
头文件：tree.h

#include<iostream>
#include<vector>
using namespace std;
struct TreeNode
{
    char value;
    vector<TreeNode*> next;
};
TreeNode* CreateTreeNode(char data, int n);
void ConnectTreeNode(TreeNode *parent, TreeNode *child, int n);
void PrintTree(TreeNode *pRoot);
void DestroyTree(TreeNode* pRoot);

源文件：tree.cpp

#include"tree.h"
TreeNode* CreateTreeNode(char data,int n)
{
    TreeNode *pRoot = new TreeNode();
    pRoot->value = data;
    pRoot->next = vector<TreeNode*>(n, NULL);
    return pRoot;
}
void ConnectTreeNode(TreeNode *parent, TreeNode *child, int n)
{
    if (parent != NULL)
    {
        parent->next[n-1] = child;
    }
}
void PrintTree(TreeNode *pRoot)
{
    if (pRoot)
    {
        cout << pRoot->value << endl;
        for (int i = 0; i < pRoot->next.size(); i++)
        {
            if (pRoot->next[i])
            {
                cout << pRoot->value << "第" << i + 1 << "个结点:" << pRoot->next[i]->value << endl;
            }
        }
        if (pRoot->next.size() == 0)
        {
            cout << pRoot->value << "没有子结点！"<< endl;
        }
        cout << endl;
        //
        for (int i = 0; i < pRoot->next.size(); i++)
        {
            PrintTree(pRoot->next[i]);
        }
    }
}
void DestroyTree(TreeNode* pRoot)
{
    if (pRoot != NULL)
    {
        vector<TreeNode*> temp = pRoot->next;
        delete pRoot;
        for (int i = 0; i < temp.size(); i++)
            DestroyTree(temp[i]);
        pRoot = NULL;
    }
}

主函数：main.cpp

//面试题50—树中两个节点的最低公共祖先
//示例代码：
#include<iostream>
#include"tree.h"
using namespace std;
bool CommonParentNode(TreeNode *pRoot, TreeNode* node,vector<TreeNode*>&path)
{
    if (pRoot == node)
        return true;
    path.push_back(pRoot);
    bool found = false;
    int i = 0;
    int n = pRoot->next.size();
    while (!found&&i < n)
    {
        found = CommonParentNode(pRoot->next[i], node, path);
        i++;
    }
    if (!found)
        path.pop_back();
    return found;

}
TreeNode* CommonParentNode(vector<TreeNode*>path1, vector<TreeNode*>path2)
{
    int i = 0;
    int n1 = path1.size();
    int n2 = path2.size();
    while (i < n1&&i < n2)
    {
        if (path1[i] == path2[i])
            i++;
        else
            break;
    }
    if (i == 0)
    {
        return NULL;
    }
    else
    {
        return path1[i - 1];
    }
}

int main()
{
    TreeNode *p1 = CreateTreeNode('A', 2);
    TreeNode *p2 = CreateTreeNode('B', 2);
    TreeNode *p3 = CreateTreeNode('C', 0);
    TreeNode *p4 = CreateTreeNode('D', 2);
    TreeNode *p5 = CreateTreeNode('E', 3);
    TreeNode *p6 = CreateTreeNode('F', 0);
    TreeNode *p7 = CreateTreeNode('G', 0);
    TreeNode *p8 = CreateTreeNode('H', 0);
    TreeNode *p9 = CreateTreeNode('I', 0);
    TreeNode *p10 = CreateTreeNode('J', 0);
    //
    ConnectTreeNode(p1, p2, 1);
    ConnectTreeNode(p1, p3, 2);
    ConnectTreeNode(p2, p4, 1);
    ConnectTreeNode(p2, p5, 2);
    ConnectTreeNode(p4, p6, 1);
    ConnectTreeNode(p4, p7, 2);
    ConnectTreeNode(p5, p8, 1);
    ConnectTreeNode(p5, p9, 2);
    ConnectTreeNode(p5, p10, 3);
    //===
    //PrintTree(p1);
    //===
    vector<TreeNode*> path1;
    vector<TreeNode*>path2;
    bool found1 = CommonParentNode(p1, p4, path1);
    bool found2 = CommonParentNode(p1, p5, path2);

    for (int i = 0; i < path1.size(); i++)
        cout << path1[i]->value << "";
    if (found1&&found2)
    {
        TreeNode *res = CommonParentNode(path1, path2);
        if (res)
            cout << "最低共同祖先结点：" << res->value << endl;
        else
            cout << "没有共同祖先结点！" << endl;
    }
    DestroyTree(p1);
}