[leetCode] Recover Binary Search Tree

class Solution {
    public:
        void recoverTree(TreeNode *root) {
            vector<TreeNode*> result;
            stack<TreeNode*> st;

            TreeNode* p = root;

            // inorder traverse
            while(p != NULL || st.size() != 0)
            {
                while(p != NULL)
                {
                    st.push(p);
                    p = p->left;
                }

                if(!st.empty())
                {
                    p = st.top();
                    st.pop();
                    result.push_back(p);
                    p = p->right;
                }
            }

            TreeNode* r1 = NULL, *r2 = NULL;
            for(int i = 0; i < result.size()-1; i++)
            {
                if(result[i]->val  > result[i+1]->val)
                {
                    r1 = result[i];
                    break;
                }
            }

            for(int i = result.size()-1; i >= 1; i--)
            {
                if(result[i]->val < result[i-1]->val)
                {
                    r2 = result[i];
                    break;
                }
            }
            //swap r1 and r2's value

            int tmp = r1->val;
            r1->val = r2->val;
            r2->val = tmp;
        }
};