diff --git a/algorithms/bestTimeToBuyAndSellStock/bestTimeToBuyAndSellStock.cpp b/algorithms/bestTimeToBuyAndSellStock/bestTimeToBuyAndSellStock.cpp
index e6bc986b1..f10321f86 100644
--- a/algorithms/bestTimeToBuyAndSellStock/bestTimeToBuyAndSellStock.cpp
+++ b/algorithms/bestTimeToBuyAndSellStock/bestTimeToBuyAndSellStock.cpp
@@ -25,28 +25,13 @@ class Solution {
     // Notes:
     //    Some people think find the highest-price & lowest-price, this is wrong. 
     //    Because the highest-price must be after lowest-price
-    //
     int maxProfit(vector<int> &prices) {
-        
-        int max=0, begin=0, end=0, delta=0;
-        
+        if(prices.size() == 0) return 0;
+        int MAX=0, MIN=prices[0];
         for (int i=0; i<prices.size(); i++) {
-            
-            end = i;
-            
-            delta = prices[end] - prices[begin];
-            
-            if (delta <= 0){
-                begin = i;
-            }
-            
-            if ( delta > max ){
-                max = delta;
-            }
-            
+            MIN = min(MIN, prices[i]);
+            MAX = max(MAX, prices[i] - MIN);
         }
-        
-        return max;
-        
+        return MAX;
     }
 };
diff --git a/algorithms/kthSmallestElementInaBST/KthSmallestElementInABst.cpp b/algorithms/kthSmallestElementInaBST/KthSmallestElementInABst.cpp
index fd3581b50..15f450cb3 100644
--- a/algorithms/kthSmallestElementInaBST/KthSmallestElementInABst.cpp
+++ b/algorithms/kthSmallestElementInaBST/KthSmallestElementInABst.cpp
@@ -49,20 +49,17 @@ class Solution {
     // in-order travel - non-recursive way
     int kthSmallestHelper_nonRecursive(TreeNode* root, int k){
         stack<TreeNode*> s;
-        
         while(!s.empty() || root){
-            
-            while (root) { 
+            if(root){
                 s.push(root);
-                root = root->left;
+                root = root -> left;
+            }else{
+                root = s.top();
+                s.pop();
+                k--;
+                if(k==0) return root -> val;
+                root = root -> right;
             }
-            
-            k--;
-            root = s.top()->right;
-
-            if (k==0) return s.top()->val;
-            
-            s.pop();
         }
         return -1;
     }