func max(a, b int) int {

  if a > b {

    return a

  }

  return b

}

//121. 买卖股票的最佳时机

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]

}

//122. 买卖股票的最佳时机 II

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]

}

//123. 买卖股票的最佳时机 III

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]

}