leetcode 121. Best Time to Buy and Sell Stock

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.

数组是每天的股票价格，问在最低价买入最高价卖出的收益，注意卖出的时间要在买入的后面

思路：
顺序访问数组，更新最低价，同时更新最大收益(price[i] - 最低价）

    public int maxProfit(int[] prices) {
        if(prices == null || prices.length == 0) {
            return 0;
        }
        
        int minV = prices[0];
        int result = 0;
        
        for(int i = 1; i < prices.length; i++) {
            result = Math.max(result, prices[i] - minV);
            minV = Math.min(minV, prices[i]);
        }
        
        return result;
    }