题目：
题解：
func maxProfit(prices []int) int {
buy1, sell1 := -prices[0], 0
buy2, sell2 := -prices[0], 0
for i := 1; i < len(prices); i++ {
buy1 = max(buy1, -prices[i])
sell1 = max(sell1, buy1+prices[i])
buy2 = max(buy2, sell1-prices[i])
sell2 = max(sell2, buy2+prices[i])
}
return sell2
}
func max(a, b int) int {
if a > b {
return a
}
return b
}