func max(a, b int) int {
if a > b {
return a
}
return b
}
func maxProfit1(prices []int) int {
n := len(prices)
dp := make([][]int, n)
for i := 0; i < n; i++ {
dp[i] = make([]int, 2)
}
dp[0][0] = -prices[0]
dp[0][1] = 0
for i := 1; i < n; i++ {
//买入后利润
dp[i][0] = max(dp[i-1][0], -prices[i])
//不持有的利润
dp[i][1] = max(dp[i-1][1], dp[i-1][0]+prices[i])
}
return dp[n-1][1]
}
func maxProfit2(prices []int) int {
n := len(prices)
dp := make([][]int, n)
for i := 0; i < n; i++ {
dp[i] = make([]int, 2)
}
dp[0][0] = -prices[0]
dp[0][1] = 0
for i := 1; i < n; i++ {
//买入后利润
dp[i][0] = max(dp[i-1][0], dp[i-1][1]-prices[i])
//不持有的利润
dp[i][1] = max(dp[i-1][1], dp[i-1][0]+prices[i])
}
return dp[n-1][1]
}
func maxProfit3(prices []int) int {
n := len(prices)
dp := make([][]int, n)
for i := 0; i < n; i++ {
dp[i] = make([]int, 5)
}
dp[0][1] = -prices[0]
dp[0][3] = -prices[0]
for i := 1; i < n; i++ {
//第一次买入后的利润
dp[i][1] = max(dp[i-1][1], -prices[i])
//第一次不持有的利润
dp[i][2] = max(dp[i-1][2], dp[i-1][1]+prices[i])
//第二次买入后的利润
dp[i][3] = max(dp[i-1][3], dp[i-1][2]-prices[i])
//第二次不持有的利润
dp[i][4] = max(dp[i-1][4], dp[i-1][3]+prices[i])
}
return dp[n-1][4]
}