121. Best Time to Buy and Sell Stock

Say you have an array for which the i th element is the price of a given stock on day i.

If you were only permitted to complete at most one transaction (i.e., buy one and sell one share of the stock), design an algorithm to find the maximum profit.

Note that you cannot sell a stock before you buy one.

Example 1:

Input: [7,1,5,3,6,4]
Output: 5
Explanation: Buy on day 2 (price = 1) and sell on day 5 (price = 6), profit = 6-1 = 5.
             Not 7-1 = 6, as selling price needs to be larger than buying price.

Example 2:

Input: [7,6,4,3,1]
Output: 0
Explanation: In this case, no transaction is done, i.e. max profit = 0.

# @lc code=start
using LeetCode

function max_profit_121(prices::Vector{Int})::Int
    min_cost, profit = prices[1], 0
    for price in @view prices[2:end]
        profit = max(profit, price - min_cost)
        min_cost = min(min_cost, price)
    end
    return profit
end

# @lc code=end

max_profit_121 (generic function with 1 method)

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