LeetCode 121. Best Time to Buy and Sell Stock

[Woodyiiiiiii]

Say you have an array for which the ith 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.

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这道题实际上就是寻找当前最小值和最大值的问题。最大值要在最小值之后。

class Solution {
    public int maxProfit(int[] prices) {
        int res = 0, minPrices = Integer.MAX_VALUE;
        for (int p : prices) {
            minPrices = Math.min(minPrices, p);
            res = Math.max(res, p - minPrices);
        }
        return res;
    }
}

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参考资料:

• LeetCode原题
• [LeetCode] 121. Best Time to Buy and Sell Stock grandyang/leetcode#121