From f66b52538637e7881d85de4f82d6db302f50b7d1 Mon Sep 17 00:00:00 2001
From: YunMao <china.tianyu.dai@gmail.com>
Date: Sun, 27 Dec 2020 22:05:59 +0000
Subject: [PATCH] =?UTF-8?q?=E6=9B=B4=E6=96=B00188?=
MIME-Version: 1.0
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---
 Readme.md             |  3 +++
 yunmao/src/L0188.java | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+)
 create mode 100644 yunmao/src/L0188.java

diff --git a/Readme.md b/Readme.md
index 2f88c83..b2f5dbc 100644
--- a/Readme.md
+++ b/Readme.md
@@ -6,6 +6,9 @@
 
 - [解法1](./yunmao/src/L0085.java) 极其暴力的解法，空间和时间都很不好。
 
+### 0188
+
+- [解法1](./yunmao/src/L00188.java) 官方题解方法。
 
 ### 0205
 
diff --git a/yunmao/src/L0188.java b/yunmao/src/L0188.java
new file mode 100644
index 0000000..dec0442
--- /dev/null
+++ b/yunmao/src/L0188.java
@@ -0,0 +1,37 @@
+import java.util.Arrays;
+
+public class L0188 {
+    public static void main(String[] args) throws Exception {
+        int k = 2;
+        int[] prices = { 2, 4, 1 };
+
+        System.out.print(maxProfit(k, prices));
+    }
+
+    public static int maxProfit(int k, int[] prices) {
+
+        if (prices.length == 0) {
+            return 0;
+        }
+
+        int num = prices.length;
+        int[][] buy = new int[num][k + 1]; // 对于第j次选择在第i天买入
+        int[][] sell = new int[num][k + 1];// 对于第j次选择在第i天卖出
+
+        int i, j;
+        for (i = 0; i <= k; ++i) {
+            buy[0][i] = -prices[0];// 第i次选择在第0天买入，此时有的钱为第0天前的负数；
+            sell[0][i] = 0;// 第i次选择在第0天卖出，此时赚的钱为0；
+        }
+
+        for (i = 1; i < num; ++i) {
+            buy[i][0] = Math.max(buy[i - 1][0], sell[i - 1][0] - prices[i]); // 第0次选择在第i天买，max{第0次在i-1天买，
+                                                                             // 第0次在第i-1天处于卖出状态减去第i天的钱}
+            for (j = 1; j <= k; ++j) {
+                buy[i][j] = Math.max(buy[i - 1][j], sell[i - 1][j] - prices[i]);
+                sell[i][j] = Math.max(sell[i - 1][j], buy[i - 1][j - 1] + prices[i]);
+            }
+        }
+        return Arrays.stream(sell[num - 1]).max().getAsInt();
+    }
+}
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