package jjn.carl.dp;
import java.util.Scanner;
/** * @author Jjn * @since 2023/8/22 23:36 */public class LeetCode121 {    public int maxProfit(int[] prices) {        if (prices == null || prices.length == 0) return 0;        int length = prices.length;        // dp[i][0]代表第i天持有股票的最大收益        // dp[i][1]代表第i天不持有股票的最大收益        int[][] dp = new int[length][2];        dp[0][0] = -prices[0];        dp[0][1] = 0;        for (int i = 1; i < length; i++) {            dp[i][0] = Math.max(dp[i - 1][0], -prices[i]);            dp[i][1] = Math.max(dp[i - 1][0] + prices[i], dp[i - 1][1]);        }        return dp[length - 1][1];    }        public static void main(String[] args) {        Scanner scanner = new Scanner(System.in);        int count = scanner.nextInt();        int[] prices = new int[count];        for (int i = 0; i < count; i++) {            prices[i] = scanner.nextInt();        }        int maxProfit = new LeetCode121().maxProfit(prices);        System.out.println(maxProfit);    }}

package jjn.carl.dp;
import java.util.Scanner;
/** * @author Jjn * @since 2023/8/22 23:43 */public class LeetCode122 {    public int maxProfit(int[] prices) {        int n = prices.length;        // 创建二维数组存储状态        int[][] dp = new int[n][2];        // 初始状态        dp[0][0] = 0;        dp[0][1] = -prices[0];        for (int i = 1; i < n; ++i) {            // 第 i 天，没有股票            dp[i][0] = Math.max(dp[i - 1][0], dp[i - 1][1] + prices[i]);            // 第 i 天，持有股票            dp[i][1] = Math.max(dp[i - 1][1], dp[i - 1][0] - prices[i]);        }        return dp[n - 1][0];    }        public static void main(String[] args) {        Scanner scanner = new Scanner(System.in);        int count = scanner.nextInt();        int[] prices = new int[count];        for (int i = 0; i < count; i++) {            prices[i] = scanner.nextInt();        }        int maxProfit = new LeetCode122().maxProfit(prices);        System.out.println(maxProfit);    }}