LeetCode: Best Time to Buy and Sell Stock

// https://code.dennyzhang.com/best-time-to-buy-and-sell-stock
// Basic Ideas: greedy
//
// Complexity: Time O(n), Space O(1)
func maxProfit(prices []int) int {
    min := 1<<31-1
    res := 0
    for _, val := range prices {
        // min cost so far
        if val-min > res {
            res = val-min
        }
        if val < min {
            min = val
        }
    }
    return res
}

## https://code.dennyzhang.com/best-time-to-buy-and-sell-stock
class Solution(object):
    def maxProfit(self, prices):
        """
        :type prices: List[int]
        :rtype: int
        """
        ## Idea: Suppose L is separated by L1 and L2.
        ##       If the max_profit happens in between L1 and L2,
        ##       it means we buy with some price in L1, then seel with some price in L2.
        ##       The buy price will be the mininum value within L1
        ##        
        ##
        ##       Here we suppose to scan the list only once
        ##
        ##       max_profit: best deal within L1
        ##       min_value: the mininum price within L1
        ##           
        ##       
        ## Complexity: Time O(n), Space O(1)
        ## Sample Data:
        ##     7, 1, 5, 3, 6, 4
        ##
        length = len(prices)
        if length < 2:
            return 0
        min_value = prices[0]
        max_profit = -1
        for i in range(1, length):
            if prices[i] < min_value:
                min_value = prices[i]
            elif prices[i] > min_value and prices[i] - min_value > max_profit:
                max_profit = prices[i] - min_value
        return max_profit if max_profit > 0 else 0