【数据结构】二叉树搜索树（二叉排序树）BST专题

46. 二叉搜索树的后序遍历序列

class Solution {
public:
    vector<int> seq;
    bool verifySequenceOfBST(vector<int> sequence) {
        seq = sequence;
        return dfs(0, seq.size() - 1);
    }

    bool dfs(int l, int r)
    {
        if (l >= r) return true;
        int root = seq[r]; // 后序遍历的最后一个元素为根节点
        int k = l;
        while (k < r && seq[k] < root) k ++ ;
        for (int i = k; i < r; i ++ )
            if (seq[i] < root) 
                return false;

        return dfs(l, k - 1) && dfs(k, r - 1);
    }
};