查找树中元素的级别

如何解决查找树中元素的级别

所以我遇到了这个问题，我应该在树中找到元素的级别。似乎什么都没有解决，所以即时通讯在这里寻求帮助。

这是我到目前为止所得到的。这里的问题是第四个断言（假定返回的级别为2）不起作用，并且断言被警告。我想过也许不尝试递归地做，但是那怎么办呢？

int findElementLevel(const BSTree tree,const int element) {

    int level = 0;

    if (tree == NULL) {
        return -1;
    }

    if (tree->data == element) {
        return level;
    }

    if (element < (tree)->data) {
        level++;
        findElementLevel(tree->left,element);
        return level;
    }

    if (element > (tree)->data) {
        level++;
        findElementLevel(tree->right,element);
        return level;
    }
}

void testNewTree(void) {

    BSTree tree = emptyTree();
    assert(isEmpty(tree));

    int arr[5] = {3,2,5,1,4},i;

    for (i = 0; i < 5; i++)
    {
        insertSorted(&tree,arr[i]);
    }

    assert(findElementLevel(tree,3) == 0);

    assert(findElementLevel(tree,2) == 1);

    assert(findElementLevel(tree,5) == 1);

    assert(findElementLevel(tree,1) == 2);

    assert(findElementLevel(tree,4) == 2);

}

解决方法

该函数始终从设置为0的局部变量级别的声明开始。

int findElementLevel(const BSTree tree,const int element) {

    int level = 0;

如果在任何实际级别中找到目标元素，则返回该值0（或由于当前递归函数调用中的增量而为1）。

if (tree->data == element) {
    return level;
}

您必须积累水平。

例如，可以通过以下方式定义递归函数

int findElementLevel(const BSTree tree,const int element) {
    if (tree == NULL) {
        return -1;
    }
    else  if ( element < tree->data ) {
        int level = findElementLevel(tree->left,element);
        return level == -1 ? level : level + 1;
    }
    else if ( tree->data < element ) {
        int level = findElementLevel(tree->right,element);
        return level == -1 ? level : level + 1;
    }
    else {
        return 0;
    } 
}

请注意，第二个参数的限定符const意义不大，因为该函数处理的是提供的参数值的副本。函数可以像

一样声明

int findElementLevel(const BSTree tree,int element);

,

此函数比递归地更容易迭代编写。代码就是：

int findElementLevel(const BSTree tree,const int element)
{
    for (int level = 0; tree; ++level)
    {
        if (tree->data == element)
            return level;
        tree = tree->data < element ? tree->left : tree->right;
    }
    return -1;
}

有解释，它是：

int findElementLevel(const BSTree tree,const int element)
{
    /*  Use a loop to process each level.  We start counting levels at zero and
        increment on each iteration.  We continue as long as there is more of
        the tree to explore ("tree" evaluates as true,i.e.,non-null),or jump
        out of the loop with a return if the target element is found.
    */
    for (int level = 0; tree; ++level)
    {
        //  If we found the target,return the level it is on.
        if (tree->data == element)
            return level;

        /*  Otherwise,descend to the left or the right according to which
            side the target element must be on.
        */
        tree = tree->data < element ? tree->left : tree->right;
    }

    /*  If we reached the end of the tree without finding the element,return
        -1.
    */
    return -1;
}