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refactor 188
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  • src/main/java/com/fishercoder/solutions

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package com.fishercoder.solutions;
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/**
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188. Best Time to Buy and Sell Stock IV
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Say you have an array for which the ith element is the price of a given stock on day i.
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Design an algorithm to find the maximum profit. You may complete at most k transactions.
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Note:
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You may not engage in multiple transactions at the same time (ie, you must sell the stock before you buy again).
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Example 1:
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Input: [2,4,1], k = 2
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Output: 2
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Explanation: Buy on day 1 (price = 2) and sell on day 2 (price = 4), profit = 4-2 = 2.
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Example 2:
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Input: [3,2,6,5,0,3], k = 2
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Output: 7
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Explanation: Buy on day 2 (price = 2) and sell on day 3 (price = 6), profit = 6-2 = 4.
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Then buy on day 5 (price = 0) and sell on day 6 (price = 3), profit = 3-0 = 3.
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*/
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public class _188 {
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public static class Solution1 {
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/** credit: https://discuss.leetcode.com/topic/8984/a-concise-dp-solution-in-java */
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public int maxProfit(int k, int[] prices) {
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int len = prices.length;
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if (k >= len / 2) {
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return quickSolve(prices);
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}
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int[][] t = new int[k + 1][len];
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for (int i = 1; i <= k; i++) {
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int tmpMax = -prices[0];
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for (int j = 1; j < len; j++) {
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t[i][j] = Math.max(t[i][j - 1], prices[j] + tmpMax);
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tmpMax = Math.max(tmpMax, t[i - 1][j - 1] - prices[j]);
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public static class Solution1 {
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/**
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* credit: https://discuss.leetcode.com/topic/8984/a-concise-dp-solution-in-java
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*/
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public int maxProfit(int k, int[] prices) {
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int len = prices.length;
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if (k >= len / 2) {
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return quickSolve(prices);
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}
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int[][] t = new int[k + 1][len];
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for (int i = 1; i <= k; i++) {
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int tmpMax = -prices[0];
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for (int j = 1; j < len; j++) {
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t[i][j] = Math.max(t[i][j - 1], prices[j] + tmpMax);
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tmpMax = Math.max(tmpMax, t[i - 1][j - 1] - prices[j]);
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}
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}
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return t[k][len - 1];
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}
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}
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return t[k][len - 1];
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}
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private int quickSolve(int[] prices) {
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int len = prices.length;
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int profit = 0;
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for (int i = 1; i < len; i++) {
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// as long as there is a price gap, we gain a profit.
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if (prices[i] > prices[i - 1]) {
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profit += prices[i] - prices[i - 1];
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private int quickSolve(int[] prices) {
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int len = prices.length;
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int profit = 0;
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for (int i = 1; i < len; i++) {
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// as long as there is a price gap, we gain a profit.
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if (prices[i] > prices[i - 1]) {
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profit += prices[i] - prices[i - 1];
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}
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}
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return profit;
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}
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}
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return profit;
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}
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}
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}

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