From b91141ada6df34e1f1e4b6fb0e09ea31b1d64a3b Mon Sep 17 00:00:00 2001
From: Jerry-306 <82520819+Jerry-306@users.noreply.github.com>
Date: Fri, 17 Sep 2021 11:07:10 +0800
Subject: [PATCH] =?UTF-8?q?0188=20=E4=B9=B0=E5=8D=96=E8=82=A1=E7=A5=A8?=
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---
 .../0188.买卖股票的最佳时机IV.md     | 25 +++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/problems/0188.买卖股票的最佳时机IV.md b/problems/0188.买卖股票的最佳时机IV.md
index bcb8a1ab..a166db72 100644
--- a/problems/0188.买卖股票的最佳时机IV.md
+++ b/problems/0188.买卖股票的最佳时机IV.md
@@ -280,6 +280,7 @@ Go：
 Javascript：
 
 ```javascript
+// 方法一：动态规划
 const maxProfit = (k,prices) => {
     if (prices == null || prices.length < 2 || k == 0) {
         return 0;
@@ -300,6 +301,30 @@ const maxProfit = (k,prices) => {
 
     return dp[prices.length - 1][2 * k];
 };
+
+// 方法二：动态规划+空间优化
+var maxProfit = function(k, prices) {
+    let n = prices.length;
+    let dp = new Array(2*k+1).fill(0);
+    // dp 买入状态初始化
+    for (let i = 1; i <= 2*k; i += 2) {
+        dp[i] = - prices[0];
+    }
+
+    for (let i = 1; i < n; i++) {
+        for (let j = 1; j < 2*k+1; j++) {
+            // j 为奇数：买入状态
+            if (j % 2) {
+                dp[j] = Math.max(dp[j], dp[j-1] - prices[i]);
+            } else {
+                // j为偶数：卖出状态
+                dp[j] = Math.max(dp[j], dp[j-1] + prices[i]);
+            }
+        }
+    }
+
+    return dp[2*k];
+};
 ```
 
 -----------------------