package question;

import java.util.Arrays;

public class Question123 {
 public static void main(String[] args) {
 int[] array = new int[]{1, 2, 3, 4, 5};
 System.out.println(new Question123().maxProfit3(array));
 }

 public int maxProfit(int[] prices) {
 if (prices == null || prices.length == 0) return 0;
 int k = 2;//最大操作次数
 int[][][] dp = new int[prices.length][2][k + 1];
 dp[0][0][0] = 0;
 dp[0][0][1] = Integer.MIN_VALUE / 2;
 dp[0][1][0] = Integer.MIN_VALUE / 2;
 dp[0][1][1] = -prices[0];
 for (int i = 1; i < prices.length; i++) {
 dp[i][1][0] = Integer.MIN_VALUE / 2;
 dp[i][0][0] = 0;
 for (int j = 1; j <= k; j++) {
 if (j > (i + 2) / 2) {
 dp[i][0][j] = Integer.MIN_VALUE / 2;
 dp[i][1][j] = Integer.MIN_VALUE / 2;
 } else {
 dp[i][0][j] = Math.max(dp[i - 1][0][j], dp[i - 1][1][j] + prices[i]);
 dp[i][1][j] = Math.max(dp[i - 1][1][j], dp[i - 1][0][j - 1] - prices[i]);
 }
 }
 }
 int max = Integer.MIN_VALUE / 2;
 for (int i : dp[prices.length - 1][0]) {
 max = Math.max(max, i);
 }
 return max;
 }

 public int maxProfit2(int[] prices) {
 int k = 2;
 int[][] dp = new int[prices.length + 1][k * 2 + 1];
 for (int i = 0; i < dp.length; i++) {
 for (int j = i + 1; j < dp[i].length; j++) {
 dp[i][j] = Integer.MIN_VALUE / 2;
 }
 }
 for (int i = 1; i < dp.length; i++) {
 //dp[i][0]=0;
 dp[i][0] = dp[i - 1][0];
 for (int j = 1; j < dp[i].length; j++) {
 dp[i][j] = Math.max(dp[i - 1][j - 1] + ((j & 1) == 1 ? -1 : 1) * prices[i - 1], dp[i - 1][j]);
 }
// dp[i][0] = dp[i - 1][0];
// dp[i][1] = Math.max(dp[i - 1][0] - prices[i - 1], dp[i - 1][1]);
// dp[i][2] = Math.max(dp[i - 1][1] + prices[i - 1], dp[i - 1][2]);
// dp[i][3] = Math.max(dp[i - 1][2] - prices[i - 1], dp[i - 1][3]);
// dp[i][4] = Math.max(dp[i - 1][3] + prices[i - 1], dp[i - 1][4]);
 }
 /*
 1, 2, 3, 4, 5

 0, f, f, f, f
 0, -1, f, f, f
 0, -1, 1, f, f
 0, -1, 2, -2, f
 0, -1, 3, -2, 2
 0, -1, 4, -2, 3
 */
 //int max = Math.max(dp[dp.length - 1][2], dp[dp.length - 1][4]);
 int max = 0;
 for (int i = 2; i < dp[dp.length - 1].length; i += 2) {
 max = Math.max(max, dp[dp.length - 1][i]);
 }
 return max;
 }

 public int maxProfit3(int[] prices) {
 int k = 2;
 int[] dp = new int[k * 2 + 1];
 Arrays.fill(dp, Integer.MIN_VALUE / 2);
 dp[0] = 0;
 for (int i = 1; i <= prices.length; i++) {
 for (int j = dp.length - 1; j > 0; j--) {
 dp[j] = Math.max(dp[j - 1] + ((j & 1) == 1 ? -1 : 1) * prices[i - 1], dp[j]);
 }
 }
 int max = 0;
 for (int i = 2; i < dp.length; i += 2) {
 max = Math.max(max, dp[i]);
 }
 return max;
 }
}