JAVA 二叉树算法 (遍历、深度、汇总求和)

• 二叉树构造类：

public class BinaryTree {

	int data; // 根节点数据
	BinaryTree left; // 左子树
	BinaryTree right; // 右子树

	public BinaryTree(int data) // 实例化二叉树类
	{
		this.data = data;
		left = null;
		right = null;
	}

	public void insert(BinaryTree root, int data) { // 向二叉树中插入子节点
		if (data > root.data) // 二叉树的左节点都比根节点小
		{
			if (root.right == null) {
				root.right = new BinaryTree(data);
			} else {
				this.insert(root.right, data);
			}
		} else { // 二叉树的右节点都比根节点大
			if (root.left == null) {
				root.left = new BinaryTree(data);
			} else {
				this.insert(root.left, data);
			}
		}
	}
}

• 二叉树遍历、深度及求和：

public class BinaryTreePreorder {
	
	private static StringBuffer current = new StringBuffer();
    private static int sum = 0;
    private static int needSum = 178;

	public static void preOrder(BinaryTree root) { //前序遍历（递归）
		if (root != null) {
			System.out.print(root.data + "-");
			preOrder(root.left);
			preOrder(root.right);
		}
	}

	public static void inOrder(BinaryTree root) { // 中序遍历

		if (root != null) {
			inOrder(root.left);
			System.out.print(root.data + "--");
			inOrder(root.right);
		}
	}

	public static void postOrder(BinaryTree root) { // 后序遍历

		if (root != null) {
			postOrder(root.left);
			postOrder(root.right);
			System.out.print(root.data + "---");
		}
	}

	public static int getDepth(BinaryTree node) {  //深度
		if (node == null) {
			return 0;
		}
		int leftDepth = 0;
		int rightDepth = 0;
		leftDepth = getDepth(node.left);
		rightDepth = getDepth(node.right);
		return (leftDepth > rightDepth ? leftDepth : rightDepth) + 1;
	}
	
	public static void visit(BinaryTree p) {  
        System.out.print(p.data + " ");  
    }  
	
	protected static void iterativePreorder(BinaryTree p) {  //前序遍历（非递归）
        Stack<BinaryTree> stack = new Stack<BinaryTree>();  
        if (p != null) {  
            stack.push(p);  
            while (!stack.empty()) {  
                p = stack.pop();  
                visit(p);  
                if (p.right != null)  
                    stack.push(p.right);  
                if (p.left != null)  
                    stack.push(p.left);  
            }  
        }  
    }  
	
	private static void sum(BinaryTree node){    //计算二叉树节点总和数为N的集合，这里N = 178
        int val = node.data;
        current.append(val+",");
        if(node.left==null && node.right==null){ //leaf here
        	sum = 0;
        	String[] nums = current.toString().split(",");
        	for (int i=0;i<nums.length;i++) {
        		sum += Integer.parseInt(nums[i]);
        	}
        	if (sum == needSum) {
        		for (int i=0;i<nums.length;i++) {
            		System.out.print(nums[i]+"-");
            	}
        	}
        }
        else{
            if(node.left!=null){
                sum(node.left);
                current.setLength(current.length()-(node.left.data+"").length()-1);
            }
            if(node.right!=null){
                sum(node.right);
                current.setLength(current.length()-(node.right.data+"").length()-1);
            }
        }
    }
	
	public static void main(String[] str) {
		int[] array = { 12, 76, 35, 22, 16, 48, 90, 46, 9, 40 };
		BinaryTree root = new BinaryTree(array[0]); // 创建二叉树
		for (int i = 1; i < array.length; i++) {
			root.insert(root, array[i]); // 向二叉树中插入数据
		}
		 System.out.println("(递归)前序遍历：");
		 preOrder(root);
		 System.out.println();
		 System.out.println("(非递归)前序遍历：");
		 iterativePreorder(root);
		 System.out.println();
		 System.out.println("中序遍历：");
		 inOrder(root);
		 System.out.println();
		 System.out.println("后序遍历：");
		 postOrder(root);
		 System.out.println();
		 System.out.println("深度：");
		 System.out.println( getDepth(root));
		 System.out.println("遍历求和，取总和为178的序列：");
		 sum(root);
	}
}

二叉树图形：