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Leetcode - 恢复二叉搜索树

程序员文章站 2022-06-17 19:48:40
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Leetcode - 恢复二叉搜索树
Leetcode - 恢复二叉搜索树

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left;
 *     public TreeNode right;
 *     public TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public void RecoverTree(TreeNode root) {
 if (root == null) {
            return;
        }
        List<int> list = new List<int>();
        Stack<TreeNode> stack = new Stack<TreeNode>();
        TreeNode node = root;
        // 中序遍历
        while (stack.Count != 0 || node != null) {
            while (node != null) {
                stack.Push(node);
                node = node.left;
            }
            node = stack.Pop();
            list.Add(node.val);
            node = node.right;
        }
        int index1 = -1, index2 = -1, value1 = -1, value2 = -1;
        int preValue = list[0], value = -1;
        // 查找出替换的索引即值
        for (int i = 1; i < list.Count; i++) {
            value = list[i];
            if (preValue > value) {
                if (index1 == -1) {
                    index1 = i - 1;
                    value1 = preValue;
                    // 替换的位置相邻
                    index2 = i;
                    value2 = value;
                } else {
                    index2 = i;
                    value2 = value;
                    break;
                }
            }
            preValue = value;
        }

        // 中序遍历修正
        node = root;
        int index = 0;
        while (stack.Count != 0 || node != null) {
            while (node != null) {
                stack.Push(node);
                node = node.left;
            }
            node = stack.Pop();
            if (index == index1) {
                node.val = value2;
            } else if (index == index2) {
                node.val = value1;
                break;
            }
            node = node.right;
            index++;
        }
    }
}

Leetcode - 恢复二叉搜索树

相关标签: Leetcode练习