add a new simpler solution

wangxin311 · Feb 2, 2019 · 4d762f4 · 4d762f4
1 parent 7249bc3
commit 4d762f4
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Showing 2 changed files with 32 additions and 2 deletions.
diff --git a/algorithms/cpp/bestTimeToBuyAndSellStock/bestTimeToBuyAndSellStock.II.cpp b/algorithms/cpp/bestTimeToBuyAndSellStock/bestTimeToBuyAndSellStock.II.cpp
@@ -15,11 +15,15 @@
 
 class Solution {
 public:
-    //
+    int maxProfit(vector<int>& prices) {
+        return maxProfit02(prices);
+        return maxProfit01(prices);
+    }
+    // Solution 1 
     // find all of ranges: which start a valley with the nearest peak after
     // add their delta together 
     //
-    int maxProfit(vector<int> &prices) {
+    int maxProfit01(vector<int> &prices) {
 
         int max = 0;
         int low = -1;
@@ -43,4 +47,14 @@ class Solution {
 
         return max;
     }
+
+    // Solution 2 
+    // if we find we can earn money, we just sell
+    int maxProfit02(vector<int>& prices) {
+        int profit = 0 ;
+        for(int i=1; i< prices.size(); i++) {
+            profit += max(0, prices[i] - prices[i-1]);
+        }
+        return profit;
+    }
 };
diff --git a/algorithms/cpp/bestTimeToBuyAndSellStock/bestTimeToBuyAndSellStock.cpp b/algorithms/cpp/bestTimeToBuyAndSellStock/bestTimeToBuyAndSellStock.cpp
@@ -50,3 +50,19 @@ class Solution {
 
     }
 };
+
+
+class Solution {
+public:
+    int maxProfit(vector<int>& prices) {
+        int buy = INT_MAX;
+        int profit = 0;
+        for (auto p : prices) {
+    	    // Keep tracking the previous lowest price
+            buy = min (buy, p);
+	    // Keep tacking the current max profit
+            profit = max(profit, p - buy);
+        }
+        return profit;
+    }
+};