本演示程序中，集合的元素为字符，集合大小为n<20，以字符串的形式输入，以“回车”为结束标志。程序读入一个字符串，统计该字符串中出现的字符及其次数，然后输出结果。运用一个二叉树来保存处理结果，字符串中的每个不同的字符用树描述，每个结点包含4 个域，格式为：

字符

该字符的出现次数

指向ASCII码小于该字符的左子树指针

指向ASCII码大于该字符的右子树指针

因此，程序的功能是依次从输入字符串中取出一个字符，把它们插入到树中

-The demonstration program, a collection of elements for the characters, set the size of n <20, in the form of input string in order to　return　to end the signs. Program read into a string, statistics appear in the string of characters and their number, and then output the results. Using a binary tree to save the results, each string of characters with different tree descr iption, each node contains four domains, the format is: the emergence of characters in the number of characters in ASCII code point is less than the characters left subtree pointer to ASCII character code is greater than the right subtree pointer, therefore, the procedure followed by the function is removed from the input string one character, they are inserted into the tree