[leetcode]Best Time to Buy and Sell Stock

一趟遍历。O(n)。期间记录最小的价格min的值并不断比较更新最大差价。

public class Solution {
    public int maxProfit(int[] prices) {
        // Start typing your Java solution below
        // DO NOT write main() function
        if (prices.length < 2) return 0;
        
        int min = prices[0];
        int max = 0;
        for (int i = 1; i < prices.length; i++) {
            if (prices[i] < min) {
        		min = prices[i];
        	}
        	else
        	{
        		int val = prices[i] - min;
        		if (val > max) max = val;
        	}
        }
        return max;
    }
}

第二刷：

class Solution {
public:
    int maxProfit(vector<int> &prices) {
        int m = 0;
        if (prices.size() == 0)
            return m;
        int minPrice = prices[0];
        for (int i = 0; i < prices.size(); i++) {
            if (prices[i] < minPrice)
                minPrice = prices[i];
            int x = prices[i] - minPrice;
            if (x > m)
                m = x;
        }
        return m;
    }
};