java刷题-剑指offer 07 重建二叉树

Posted 2021-06-28 Anrys

java刷题-剑指offer 07 重建二叉树

• 题目
• 代码
• 结果

题目

代码

class Solution {
    public TreeNode buildTree(int[] preorder, int[] inorder) {
        int n = preorder.length;
        if (n == 0) return null;
        int rootVal = preorder[0], rootIndex = 0;
        for (int i = 0; i < n; i++) {  //先遍历中序数组找到根节点所在位置
            if (inorder[i] == rootVal) {
                rootIndex = i;
                break;
            }
        }
        TreeNode root = new TreeNode(rootVal);
        root.left = buildTree(Arrays.copyOfRange(preorder, 1, 1 + rootIndex), //左子树是从左子树节点开始递归
                                Arrays.copyOfRange(inorder, 0, rootIndex));
        root.right = buildTree(Arrays.copyOfRange(preorder, 1 + rootIndex, n), //右子树是从右子树节点开始递归
                                Arrays.copyOfRange(inorder, rootIndex + 1, n));
        return root;
    }
}

结果