题解 | 寻找下一个结点

/*
struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
    TreeNode(int x) :
            val(x), left(NULL), right(NULL) {
    }
};*/

class Successor {
    int helper(TreeNode* root, int p, bool &sign){
        if(!root) return -1;
        int left = helper(root->left, p, sign);
        if(left != -1) {
            return left;
        }
        if(sign){
            return root->val;
        }
        if(root->val == p){
            sign = true;
        }
        return helper(root->right, p, sign);
    }
public:
    int findSucc(TreeNode* root, int p) {
        // write code here
        bool sign = false;
        return helper(root, p, sign);
    }
};