From 1d364bcad49ccd341ba68ad4c31c4b0636a9cab9 Mon Sep 17 00:00:00 2001
From: crupest <crupest@outlook.com>
Date: Sun, 20 Sep 2020 22:59:35 +0800
Subject: import(solutions): Add problem 123 .

---
 works/solutions/cpp/123.cpp | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 works/solutions/cpp/123.cpp

(limited to 'works/solutions/cpp/123.cpp')

diff --git a/works/solutions/cpp/123.cpp b/works/solutions/cpp/123.cpp
new file mode 100644
index 0000000..f4feff2
--- /dev/null
+++ b/works/solutions/cpp/123.cpp
@@ -0,0 +1,34 @@
+#include <vector>
+#include <iostream>
+using std::vector;
+
+#include <algorithm>
+
+class Solution
+{
+public:
+    // 0 -> after buy for the first time
+    // 1 -> after sell for the first time
+    // 2 -> after buy for the second time
+    // 3 -> after sell for the second time
+
+    int maxProfit(vector<int> &prices)
+    {
+        int day_count = prices.size();
+
+        int state_0 = -prices[0];
+        int state_1 = 0;
+        int state_2 = -prices[0];
+        int state_3 = 0;
+
+        for (int day = 1; day < day_count; day++)
+        {
+            state_0 = std::max(state_0, -prices[day]);
+            state_1 = std::max(state_1, state_0 + prices[day]);
+            state_2 = std::max(state_2, state_1 - prices[day]);
+            state_3 = std::max(state_3, state_2 + prices[day]);
+        }
+
+        return std::max({state_0, state_1, state_2, state_3});
+    }
+};
-- 
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