7、重建二叉树 - 码农教程

输入某二叉树的前序遍历和中序遍历的结果，请重建出该二叉树。假设输入的前序遍历和中序遍历的结果中都不含重复的数字。例如输入前序遍历序列{1,2,4,7,3,5,6,8}和中序遍历序列{4,7,2,1,5,3,8,6}，则重建二叉树并返回。

class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;

    TreeNode(int x) {
        val = x;
    }
}

public class Sol7 {
    public TreeNode reConstructBinaryTree(int[] pre, int[] in) {
        TreeNode root = reConstructBinaryTree(pre, 0, pre.length - 1, in, 0, in.length - 1);
        return root;
    }
    
    private TreeNode reConstructBinaryTree(int[] pre, int startPre, int endPre, int[] in, int startIn, int endIn) {

        if (startPre > endPre || startIn > endIn)
            return null;
        TreeNode root = new TreeNode(pre[startPre]);

        for (int i = startIn; i <= endIn; i++)
            if (in[i] == pre[startPre]) {
                
                root.left = reConstructBinaryTree(pre, startPre + 1, startPre + i - startIn, in, startIn, i - 1);
                root.right = reConstructBinaryTree(pre, startPre + i - startIn + 1, endPre, in, i + 1, endIn);
                break;
            }
        return root;
    }
}

原文地址：https://www.cnblogs.com/Aug-20/p/11734664.html