【leetcode】121. Best Time to Buy and Sell Stock(easy)

与 53. Maximum Subarray类似。
https://blog.youkuaiyun.com/eclipse_c/article/details/88417065
Kadane算法算法的变形

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// 121. Best Time to Buy and Sell Stock
// 对于原数组，如果我们将arr[i]-arr[i-1]，也就是股票某日与前一日价格差，依次排列成一个数组，那么所求问题的答案就变成了求这个新数组的最大子列和。
int Solution::maxProfit(vector<int>& prices)
{
	int cur = 0; 
	int res = 0; // 最小为0
	for (int i = 1; i < prices.size(); ++i)
	{
		int cha = prices[i] - prices[i - 1];
		cur = std::max(cha + cur, cha);
		res = std::max(cur, res);
	}
	return res;
}

Runtime: 8 ms, faster than 99.57% of C++ online submissions for Best Time to Buy and Sell Stock.
Memory Usage: 9.6 MB, less than 18.90% of C++ online submissions for Best Time to Buy and Sell Stock.