Update 0121.卖股票的最佳时机.md 贪心以及动态规划 Go版本

problems/0121.买卖股票的最佳时机.md

@@ -311,7 +311,36 @@ class Solution:
 ```
 
 Go:
+> 贪心法：
+```Go
+func maxProfit(prices []int) int {
+    low := math.MaxInt32
+    rlt := 0
+    for i := range prices{
+        low = min(low, prices[i])
+        rlt = max(rlt, prices[i]-low)
+    }
 
+    return rlt
+}
+func min(a, b int) int {
+    if a < b{
+        return a
+    }
+
+    return b
+}
+
+func max(a, b int) int {
+    if a > b{
+        return a
+    }
+
+    return b
+}
+```
+
+> 动态规划：版本一
 ```Go
 func maxProfit(prices []int) int {
 	length:=len(prices)
@@ -338,6 +367,29 @@ func max(a,b int)int {
 }
 ```
 
+> 动态规划：版本二
+```Go
+func maxProfit(prices []int) int {
+    dp := [2][2]int{}
+    dp[0][0] = -prices[0]   
+    dp[0][1] = 0
+    for i := 1; i < len(prices); i++{
+        dp[i%2][0] = max(dp[(i-1)%2][0], -prices[i])
+        dp[i%2][1] = max(dp[(i-1)%2][1], dp[(i-1)%2][0]+prices[i])
+    }
+
+    return dp[(len(prices)-1)%2][1]
+}
+
+func max(a, b int) int {
+    if a > b{
+        return a 
+    }
+
+    return b
+}
+```
+
 JavaScript:
 
 > 动态规划