Update 0654.最大二叉树.md

添加 0654.最大二叉树 Java版本

problems/0654.最大二叉树.md

@@ -224,7 +224,35 @@ root->right = traversal(nums, maxValueIndex + 1, right);
 
 
 Java：
+```Java
+class Solution {
+    public TreeNode constructMaximumBinaryTree(int[] nums) {
+        return constructMaximumBinaryTree1(nums, 0, nums.length);
+    }
 
+    public TreeNode constructMaximumBinaryTree1(int[] nums, int leftIndex, int rightIndex) {
+        if (rightIndex - leftIndex < 1) {// 没有元素了
+            return null;
+        }
+        if (rightIndex - leftIndex == 1) {// 只有一个元素
+            return new TreeNode(nums[leftIndex]);
+        }
+        int maxIndex = leftIndex;// 最大值所在位置
+        int maxVal = nums[maxIndex];// 最大值
+        for (int i = leftIndex + 1; i < rightIndex; i++) {
+            if (nums[i] > maxVal){
+                maxVal = nums[i];
+                maxIndex = i;
+            }
+        }
+        TreeNode root = new TreeNode(maxVal);
+        // 根据maxIndex划分左右子树
+        root.left = constructMaximumBinaryTree1(nums, leftIndex, maxIndex);
+        root.right = constructMaximumBinaryTree1(nums, maxIndex + 1, rightIndex);
+        return root;
+    }
+}
+```
 
 Python：