1、求二叉树的深度
public class BinaryTreeTest { public static void main(String[] args) { Tree left = new Tree(1, null, null); Tree right = new Tree(2, null, null); Tree right1 = new Tree(3, left, right); Tree right2 = new Tree(4, null, null); Tree head = new Tree(5, right1, right2); //求二叉树的深度 int depth = getDepth(head); System.out.println(depth); } public static int getDepth(Tree root) { if(root == null){ return 0; } int left = getDepth(root.left); int right = getDepth(root.right); return Math.max(left, right) + 1; } static class Tree{ int val; Tree left; Tree right; public Tree(int val, Tree left, Tree right) { this.val = val; this.left = left; this.right = right; } } }
2、求二叉树的最小深度
3、求二叉树的叶子节点
public static int getNodeCount(Tree root){ if(root == null){ return 0; } if(root.left == null && root.right == null){ return 1; } int left = getNodeCount(root.left); int right = getNodeCount(root.right); return left + right; }
4、5、6 三种遍历二叉树的算法(前、中、后):针对的是根节点的位置
前序遍历
public static List<Integer> getPrev(Tree root) { List<Integer> nodes = new ArrayList<>(); return getNodes(root, nodes); } private static List<Integer> getNodes(Tree root, List<Integer> nodes) { if(root == null){ return nodes; } nodes.add(root.val); getNodes(root.left, nodes); getNodes(root.right, nodes); return nodes; }
中序遍历
public static List<Integer> getPrev(Tree root) { List<Integer> nodes = new ArrayList<>(); return getNodes(root, nodes); } private static List<Integer> getNodes(Tree root, List<Integer> nodes) { if(root == null){ return nodes; } getNodes(root.left, nodes); nodes.add(root.val); getNodes(root.right, nodes); return nodes; }
后序遍历