从键盘输入若干字符，统计每个字符出现的频率，将字符出现的频率作为结点的权值，建立哈夫曼树，然后对各个字符进行哈夫曼编码，最后打印输出每个字符及对应的哈夫曼编-Enter the number of characters from the keyboard, statistics, the frequency of each character, the character frequency of occurrence as the node weights to build the Huffm