如題 : 在二叉樹中查詢最大值的節點並返回

測試資料 : {1,-5,3,1,2,-4,-5}

答案 : 3

思路 : 從根節點往下分別查詢左子樹和右子樹的最大節點，再比較左子樹，右子樹，根節點的大小得到結果，在得到左子樹和右子樹最大節點的過程相似，因此可以採用遞迴的方法

//樹節點結構 public class TreeNode { TreeNode left; TreeNode right; int val; TreeNode(int val){ this.val = val; } } public class Solution { /** * @param root 傳入根節點 * @return 返回最大結果 */ public static TreeNode maxNode(TreeNode root){ //當再無子節點，返回當前節點 if (root == null) { return root; } TreeNode left = maxNode(root.left);//遞迴得到左子樹最大值 TreeNode right = maxNode(root.right);//遞迴得到右子樹的最大值 return max(root,max(left,right));//返回左節點，根節點,右節點的最大值 } public static TreeNode max(TreeNode a,TreeNode b) { if (a == null) { return b; } if (b == null) { return a; } if (a.val > b.val) { return a; } return b; } public static void main(String[] args) { TreeNode t1 = new TreeNode(1); TreeNode t2 = new TreeNode(-5); TreeNode t3 = new TreeNode(3); TreeNode t4 = new TreeNode(1); TreeNode t5 = new TreeNode(2); TreeNode t6 = new TreeNode(-4); TreeNode t7 = new TreeNode(-5); t1.left = t2;t1.right = t5; t2.left = t3;t2.right = t4; t5.left = t6;t5.right = t7; System.out.println(Solution.maxNode(t1).val); } }