//测试创建的哈夫曼树
CodeNode root = creatTree(nodeList);
// root.preOrder();
toCode(root,"",stringBuilder);
System.out.println(map);
}
//统计字符数组中字符出现的个数,存入哈市表中,并转换链表返回
public static List<CodeNode> getCodeNodes(char[] chars){
//1.创建一个Arrayslist
ArrayList<CodeNode> list = new ArrayList<>();
//2.存储每个字符出现的次数,遍历字符数组,并将其存放到hash表中
Hashtable<Character, Integer> hashtable = new Hashtable<>();
for (char ch:chars) {
Integer conuts = hashtable.get(ch);//统计ch在hashTable中出现的次数
if(conuts == null){//如果ch在hashTable中出现的次数为空,则将ch存入hashTable中,并将次数置为1
hashtable.put(ch,1);
}else {
hashtable.put(ch,conuts+1);//如果已经存在就将其的value值加一
}
}
//循环结束,对hash表进行遍历,创建节点,存到ArraysList链表中,开始构造树节点
for (Map.Entry<Character, Integer> node: hashtable.entrySet()) {
list.add(new CodeNode(node.getKey(),node.getValue()));
}
return list;
}
//创建哈夫曼树
public static CodeNode creatTree(List<CodeNode> list){
while (list.size() > 1){
Collections.sort(list);
CodeNode leftNode = list.get(0);
CodeNode rightNode = list.get(1);
int leftCount = leftNode.count;
int righrCount = rightNode.count;
CodeNode parent = new CodeNode((leftCount+righrCount));
parent.left = leftNode;
parent.right = rightNode;
list.remove(leftNode);
list.remove(rightNode);
list.add(parent);
}
return list.get(0);
}
//前序遍历
public static void preOrder(CodeNode root){
if (root != null){
root.preOrder();
}else{
System.out.println("此树为空");
}
}
//创建一个map将哈夫曼编码存放在Map<char,String>
static Map<Character,String> map = new HashMap();
//在生成哈夫曼编码时,需要拼接路径,定义一个StringBUilder存储有叶子节点的路径
static StringBuilder stringBuilder = new StringBuilder();
//将哈夫曼树转换成哈夫曼编码
public static void toCode(CodeNode node,String code,StringBuilder stringBuilder){
StringBuilder stringBuilder1 = new StringBuilder(stringBuilder);
//将code添加到stringBuilder1中。
stringBuilder1.append(code);
if(node.left == null || node.right == null){
map.put(node.c,stringBuilder1.toString());
}else {//说明已经到达叶子节点,返回结果
//向左递归
toCode(node.left,"0",stringBuilder1);
//向右递归
toCode(node.right,"1",stringBuilder1);
}
}
}
/**
-
c : 存放字符本身
-
count : 字符本身出现的次数,及权值
*/
class CodeNode implements Comparable{
char c;
int count;
CodeNode left;
CodeNode right;
面试准备+复习分享:
为了应付面试也刷了很多的面试题与资料,现在就分享给有需要的读者朋友,资料我只截取出来一部分哦
nt;
CodeNode left;
CodeNode right;
面试准备+复习分享:
为了应付面试也刷了很多的面试题与资料,现在就分享给有需要的读者朋友,资料我只截取出来一部分哦
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