搜索二叉树应用——简单字典实现

Posted 2020-10-25

搜索二叉树基本概念请看上篇博客
这两个问题都是典型的K（key）V（value）问题，我们用KV算法解决。

1. 判断一个单词是否拼写正确：假设把所有单词都按照搜索树的性质插入到搜索二叉树中，我们判断一个单词拼写是否正确就是在树中查找该单词是否存在（查找key是否存在）。

结构声明下

typedef char* KeyType;

typedef struct BSTreeNode 
{
    struct BSTreeNode *_left;
    struct BSTreeNode *_right;

    KeyType _key;
}BSTreeNode;

插入，查找函数代码如下：

int BSTreeNodeInsertR(BSTreeNode **tree,KeyType key) //搜索树的插入
{
    int tmp = 0;
    if(*tree == NULL)
    {
        *tree = BuyTreeNode(key);
        return 0;
    }

    tmp  = strcmp((*tree)->_key,key);
    if (tmp>0)
        return BSTreeNodeInsertR(&(*tree)->_left,key);
    else if (tmp<0)
        return BSTreeNodeInsertR(&(*tree)->_right,key);
    else
        return -1;
}

BSTreeNode *BSTreeNodeFindR(BSTreeNode *tree,KeyType const key) //查找
{
    int tmp = 0;
    if (!tree)
        return NULL;

    tmp = strcmp(tree->_key,key);
    if (tmp > 0)
        return BSTreeNodeFindR(tree->_left,key);
    else if (tmp < 0)
        return BSTreeNodeFindR(tree->_right,key);
    else
        return tree;
}

测试代码：

void TestApplication()
{
    BSTreeNode *tree = NULL;

    BSTreeNodeInsertR(&tree,"hello");
    BSTreeNodeInsertR(&tree,"world");
    BSTreeNodeInsertR(&tree,"int");
    BSTreeNodeInsertR(&tree,"char");
    BSTreeNodeInsertR(&tree,"float");
    BSTreeNodeInsertR(&tree,"double");

    printf("%s \n", BSTreeNodeFindR(tree,"char")->_key);
    printf("%s \n", BSTreeNodeFindR(tree,"double")->_key);
    printf("%s \n", BSTreeNodeFindR(tree,"int")->_key);
    printf("%s \n", BSTreeNodeFindR(tree,"float")->_key);
    printf("%s \n", BSTreeNodeFindR(tree,"hello")->_key);
    printf("%s \n", BSTreeNodeFindR(tree,"world")->_key);
    printf("%p \n", BSTreeNodeFindR(tree,"chars"));
    printf("%p \n", BSTreeNodeFindR(tree,"str"));
}

测试结果:

2. 请模拟实现一个简单的字典（简单的中英文字典）

结构构建

typedef char* KeyType;
typedef int ValueType;

typedef struct BSTreeNode 
{
    struct BSTreeNode *_left;
    struct BSTreeNode *_right;

    KeyType _key;
    ValueType _count;
}BSTreeNode;

查找函数与上面相同，插入函数有所改变。

int BSTreeNodeInsertR(BSTreeNode **tree,KeyType key, ValueType value) //搜索树的插入
{
    int tmp = 0;
    if(*tree == NULL)
    {
        *tree = BuyTreeNode(key,value);
        return 0;
    }

    tmp  = strcmp((*tree)->_key,key);
    if (tmp>0)
        return BSTreeNodeInsertR(&(*tree)->_left,key,value);
    else if (tmp<0)
        return BSTreeNodeInsertR(&(*tree)->_right,key,value);
    else
        return -1;
}

测试代码：

void test()
{
    BSTreeNode *tree = NULL;
    BSTreeNodeInsertR(&tree,"hello","你好");
    BSTreeNodeInsertR(&tree,"world","世界");
    BSTreeNodeInsertR(&tree,"char","字符");
    BSTreeNodeInsertR(&tree,"int","整形");
    BSTreeNodeInsertR(&tree,"float","浮点型");

    printf("%s \n", BSTreeNodeFindR(tree,"char")->_value);
    printf("%s \n", BSTreeNodeFindR(tree,"int")->_value);
    printf("%s \n", BSTreeNodeFindR(tree,"float")->_value);
    printf("%s \n", BSTreeNodeFindR(tree,"hello")->_value);
    printf("%s \n", BSTreeNodeFindR(tree,"world")->_value);
    printf("%p \n", BSTreeNodeFindR(tree,"double"));
}

测试结果

构建测试案例尽量构建全面，防止特殊情况被忽略。