Say you have an array for which the i-th element is the price of a given stock on day i.
Design an algorithm to find the maximum profit. You may complete at most k transactions.
Note:
You may not engage in multiple transactions at the same time (ie, you must sell the stock before you buy again).
Example 1:
Input: [2,4,1], k = 2 Output: 2 Explanation: Buy on day 1 (price = 2) and sell on day 2 (price = 4), profit = 4-2 = 2.
Example 2:
Input: [3,2,6,5,0,3], k = 2 Output: 7 Explanation: Buy on day 2 (price = 2) and sell on day 3 (price = 6), profit = 6-2 = 4. Then buy on day 5 (price = 0) and sell on day 6 (price = 3), profit = 3-0 = 3.
class Solution { public int maxProfit(int k, int[] prices) { int l = prices.length; if(l==0) return 0; if(k >= l) return btbs2(prices); int[][] global = new int[l][k+1]; int[][] local = new int[l][k+1]; for(int i = 1; i < l; i++){ int diff = prices[i] - prices[i-1]; for(int j = 1; j <= k; j++){ local[i][j] = Math.max(global[i-1][j-1]+Math.max(0, diff), local[i-1][j] + diff); // Math.max似乎是多余的 global[i][j] = Math.max(global[i-1][j], local[i][j]); } } return global[l-1][k]; } public int btbs2(int[] prices){ int res = 0; for(int i = 1; i < prices.length; i++){ if(prices[i] > prices[i-1]) res += prices[i] - prices[i-1]; } return res; } }
这题是真他妈难。
不错的讲解:http://www.360doc.com/content/16/1004/16/10408243_595735141.shtml
https://blog.csdn.net/linhuanmars/article/details/23236995
https://www.cnblogs.com/grandyang/p/4295761.html