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Best Time to Buy and Sell Stock I,II,III [leetcode]
Best Time to Buy and Sell Stock I
只能作一次操作时:维护preMin记录之前出现的最小值
代码如下:
int maxProfit(vector<int> &prices) { if (prices.size() == 0) return 0; int profit = 0; int preMin = prices[0]; for (int i = 1; i < prices.size(); i++) { if (prices[i] < preMin) preMin = prices[i]; profit = max(profit, prices[i] - preMin); } return profit; }
Best Time to Buy and Sell Stock II
能无限次操作时:当==>当前价格 > 买入价格的时候,卖出
代码如下:
int maxProfit(vector<int> &prices) { if (prices.size() == 0) return 0; int profit = 0; int buy = prices[0]; for (int i = 1; i < prices.size(); i++) { if (buy < prices[i]) profit += prices[i] - buy; buy = prices[i]; } return profit; }
Best Time to Buy and Sell Stock III
只能操作两次时:
两次操作不能重叠,可以分成两部分:0...i的最大利润fst 和i...n-1的最大利润snd
代码如下:
int maxProfit(vector<int> &prices) { if (prices.size() == 0) return 0; int size = prices.size(); vector<int> fst(size); vector<int> snd(size); int preMin = prices[0]; for (int i = 1; i < size; i++) { if (preMin > prices[i]) preMin = prices[i]; fst[i] = max(fst[i - 1], prices[i] - preMin); } int profit = fst[size - 1]; int postMax = prices[size - 1]; for (int i = size - 2; i >= 0; i--) { if (postMax < prices[i]) postMax = prices[i]; snd[i] = max(snd[i + 1], postMax - prices[i]); //update profit profit = max(profit, snd[i] + fst[i]); } return profit; }
Best Time to Buy and Sell Stock I,II,III [leetcode]
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