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1 | 1 | package com.fishercoder.solutions;
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2 | 2 |
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3 |
| -/** |
4 |
| -
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5 |
| - 188. Best Time to Buy and Sell Stock IV |
6 |
| -
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7 |
| - Say you have an array for which the ith element is the price of a given stock on day i. |
8 |
| -
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9 |
| - Design an algorithm to find the maximum profit. You may complete at most k transactions. |
10 |
| -
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11 |
| - Note: |
12 |
| - You may not engage in multiple transactions at the same time (ie, you must sell the stock before you buy again). |
13 |
| -
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14 |
| - Example 1: |
15 |
| - Input: [2,4,1], k = 2 |
16 |
| - Output: 2 |
17 |
| - Explanation: Buy on day 1 (price = 2) and sell on day 2 (price = 4), profit = 4-2 = 2. |
18 |
| -
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19 |
| - Example 2: |
20 |
| - Input: [3,2,6,5,0,3], k = 2 |
21 |
| - Output: 7 |
22 |
| - Explanation: Buy on day 2 (price = 2) and sell on day 3 (price = 6), profit = 6-2 = 4. |
23 |
| - Then buy on day 5 (price = 0) and sell on day 6 (price = 3), profit = 3-0 = 3. |
24 |
| -
|
25 |
| - */ |
26 | 3 | public class _188 {
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27 |
| - public static class Solution1 { |
28 |
| - /** credit: https://discuss.leetcode.com/topic/8984/a-concise-dp-solution-in-java */ |
29 |
| - public int maxProfit(int k, int[] prices) { |
30 |
| - int len = prices.length; |
31 |
| - if (k >= len / 2) { |
32 |
| - return quickSolve(prices); |
33 |
| - } |
34 |
| - |
35 |
| - int[][] t = new int[k + 1][len]; |
36 |
| - for (int i = 1; i <= k; i++) { |
37 |
| - int tmpMax = -prices[0]; |
38 |
| - for (int j = 1; j < len; j++) { |
39 |
| - t[i][j] = Math.max(t[i][j - 1], prices[j] + tmpMax); |
40 |
| - tmpMax = Math.max(tmpMax, t[i - 1][j - 1] - prices[j]); |
| 4 | + public static class Solution1 { |
| 5 | + /** |
| 6 | + * credit: https://discuss.leetcode.com/topic/8984/a-concise-dp-solution-in-java |
| 7 | + */ |
| 8 | + public int maxProfit(int k, int[] prices) { |
| 9 | + int len = prices.length; |
| 10 | + if (k >= len / 2) { |
| 11 | + return quickSolve(prices); |
| 12 | + } |
| 13 | + |
| 14 | + int[][] t = new int[k + 1][len]; |
| 15 | + for (int i = 1; i <= k; i++) { |
| 16 | + int tmpMax = -prices[0]; |
| 17 | + for (int j = 1; j < len; j++) { |
| 18 | + t[i][j] = Math.max(t[i][j - 1], prices[j] + tmpMax); |
| 19 | + tmpMax = Math.max(tmpMax, t[i - 1][j - 1] - prices[j]); |
| 20 | + } |
| 21 | + } |
| 22 | + return t[k][len - 1]; |
41 | 23 | }
|
42 |
| - } |
43 |
| - return t[k][len - 1]; |
44 |
| - } |
45 | 24 |
|
46 |
| - private int quickSolve(int[] prices) { |
47 |
| - int len = prices.length; |
48 |
| - int profit = 0; |
49 |
| - for (int i = 1; i < len; i++) { |
50 |
| - // as long as there is a price gap, we gain a profit. |
51 |
| - if (prices[i] > prices[i - 1]) { |
52 |
| - profit += prices[i] - prices[i - 1]; |
| 25 | + private int quickSolve(int[] prices) { |
| 26 | + int len = prices.length; |
| 27 | + int profit = 0; |
| 28 | + for (int i = 1; i < len; i++) { |
| 29 | + // as long as there is a price gap, we gain a profit. |
| 30 | + if (prices[i] > prices[i - 1]) { |
| 31 | + profit += prices[i] - prices[i - 1]; |
| 32 | + } |
| 33 | + } |
| 34 | + return profit; |
53 | 35 | }
|
54 |
| - } |
55 |
| - return profit; |
56 | 36 | }
|
57 |
| - } |
58 | 37 | }
|
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