android-notes/blogs/Algorithm/剑指 Offer/二叉树相关.md

二叉树相关

目录

1. 07. 重建二叉树

07. 重建二叉树

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++) {
            if (inorder[i] == rootVal) {
                rootIndex = i;
                break;
            }
        }
        TreeNode root = new TreeNode(rootVal);
        root.left = buildTree(Arrays.copyOfRange(preorder, 1, 1 + rootIndex),
                Arrays.copyOfRange(inorder, 0, rootIndex));
        root.right = buildTree(Arrays.copyOfRange(preorder, 1 + rootIndex, n),
                Arrays.copyOfRange(inorder, rootIndex + 1, n));
        return root;
    }
}