代码语言：javascript复制
package day_21_1_24;
class Node {
public char val;
public Node left;
public Node right;
public Node(char val) {
this.val = val;
}
}
public class TestTree {
public static Node build(){
//手动把一颗树构造出来
Node a = new Node('A');
Node b = new Node('B');
Node c = new Node('C');
Node d = new Node('D');
Node e = new Node('E');
Node f = new Node('F');
Node g = new Node('G');
Node h = new Node('H');
a.left = b;
a.right = c;
b.left = d;
b.right = e;
e.left = g;
g.right = h;
c.right = f;
//返回根节点
return a;
}
//求二叉树节点个数
//使用后序遍历
public static int size(Node root){
if (root == null){
return 0;
}
//访问根节点，此处的访问操作就是计数器 1
//整个树的节点个数 = 根节点个数 左子树节点的个数 右子树节点个数
return 1 size(root.left) size(root.right);
}
//求二叉树叶子节点的个数
//root叶子节点的个数 = root.left的叶子节点的个数 root.right叶子节点的个数
public static int leafSize(Node root){
if (root == null){
return 0;
}
if (root.left == null && root.right == null){
return 1;
}
return leafSize(root.left) leafSize(root.right);
}
//求二叉树第k层节点的个数
public static int kSize(Node root,int k){
if (k < 1){
return 0;
}
if (k == 1){
return 1;
}
return kSize(root.left, k-1) kSize(root.right, k-1);
}
//在二叉树中查找指定的元素
public static Node search(Node root, char toFind){
if (root == null){
return null;
}
if (root.val == toFind){
return root;
}
Node result = search(root.left, toFind);
if (result != null){
return result;
}
return search(root.right, toFind);
}
}
