algorithm-swift/ConstrunctBinaryTree.cpp at master · zyterence/algorithm-swift · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
#include <exception>
#include <cstdio>
#pragma once

struct BinaryTreeNode
{
    int                    m_nValue;
    BinaryTreeNode*        m_pLeft;
    BinaryTreeNode*        m_pRight;
};

BinaryTreeNode* CreateBinaryTreeNode(int value)
{
    BinaryTreeNode* pNode = new BinaryTreeNode();
    pNode->m_nValue = value;
    pNode->m_pLeft = nullptr;
    pNode->m_pRight = nullptr;

    return pNode;
}

void ConnectTreeNodes(BinaryTreeNode* pParent, BinaryTreeNode* pLeft, BinaryTreeNode* pRight)
{
    if(pParent != nullptr)
        {
            pParent->m_pLeft = pLeft;
            pParent->m_pRight = pRight;
        }
}

void PrintTreeNode(const BinaryTreeNode* pNode)
{
    if(pNode != nullptr)
        {
            printf("value of this node is: %d\n", pNode->m_nValue);

            if(pNode->m_pLeft != nullptr)
                printf("value of its left child is: %d.\n", pNode->m_pLeft->m_nValue);
            else
                printf("left child is nullptr.\n");

            if(pNode->m_pRight != nullptr)
                printf("value of its right child is: %d.\n", pNode->m_pRight->m_nValue);
            else
                printf("right child is nullptr.\n");
        }
    else
        {
            printf("this node is nullptr.\n");
        }

    printf("\n");
}

void PrintTree(const BinaryTreeNode* pRoot)
{
    PrintTreeNode(pRoot);

    if(pRoot != nullptr)
        {
            if(pRoot->m_pLeft != nullptr)
                PrintTree(pRoot->m_pLeft);

            if(pRoot->m_pRight != nullptr)
                PrintTree(pRoot->m_pRight);
        }
}

void DestroyTree(BinaryTreeNode* pRoot)
{
    if(pRoot != nullptr)
        {
            BinaryTreeNode* pLeft = pRoot->m_pLeft;
            BinaryTreeNode* pRight = pRoot->m_pRight;

            delete pRoot;
            pRoot = nullptr;

            DestroyTree(pLeft);
            DestroyTree(pRight);
        }
}


BinaryTreeNode* ConstructCore(int* startPreorder, int* endPreorder, int* startInorder, int* endInorder);

BinaryTreeNode* Construct(int* preorder, int* inorder, int length)
{
    if(preorder == nullptr || inorder == nullptr || length <= 0)
        return nullptr;

    return ConstructCore(preorder, preorder + length - 1,
        inorder, inorder + length - 1);
}

BinaryTreeNode* ConstructCore
(
    int* startPreorder, int* endPreorder,
    int* startInorder, int* endInorder
)
{
    // 前序遍历序列的第一个数字是根结点的值
    int rootValue = startPreorder[0];
    BinaryTreeNode* root = new BinaryTreeNode();
    root->m_nValue = rootValue;
    root->m_pLeft = root->m_pRight = nullptr;

    if(startPreorder == endPreorder)
    {
        if(startInorder == endInorder && *startPreorder == *startInorder)
            return root;
//        else
//            throw std::exception("Invalid input.");
    }

    // 在中序遍历中找到根结点的值
    int* rootInorder = startInorder;
    while(rootInorder <= endInorder && *rootInorder != rootValue)
        ++ rootInorder;

//    if(rootInorder == endInorder && *rootInorder != rootValue)
//        throw std::exception("Invalid input.");

    int leftLength = rootInorder - startInorder;
    int* leftPreorderEnd = startPreorder + leftLength;
    if(leftLength > 0)
    {
        // 构建左子树
        root->m_pLeft = ConstructCore(startPreorder + 1, leftPreorderEnd,
            startInorder, rootInorder - 1);
    }
    if(leftLength < endPreorder - startPreorder)
    {
        // 构建右子树
        root->m_pRight = ConstructCore(leftPreorderEnd + 1, endPreorder,
            rootInorder + 1, endInorder);
    }

    return root;
}