例题列表

1049. 大盗阿福（其实就是打家劫舍）

https://www.acwing.com/activity/content/problem/content/1287/
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就是打家劫舍那道题。

对当前的房间选择抢或者不抢。

import java.io.BufferedInputStream;
import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sin = new Scanner(new BufferedInputStream(System.in));
        int t = sin.nextInt();
        while (t-- != 0) {
            int n = sin.nextInt();
            int second = 0, pre = sin.nextInt();
            for (int i = 1; i < n; ++i) {
                int temp = pre;
                pre = Math.max(pre, second + sin.nextInt());
                second = temp;
            }
            System.out.println(pre);
        }
    }
}

1057. 股票买卖 IV（k笔交易）

https://www.acwing.com/problem/content/1059/

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dp 数组多开一维表示第几笔交易就好了。

import java.io.BufferedInputStream;
import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sin = new Scanner(new BufferedInputStream(System.in));
        int n = sin.nextInt(), k = sin.nextInt();
        int[] prices = new int[n];
        for (int i = 0; i < n; ++i) prices[i] = sin.nextInt();
        int[][] buy = new int[n][k], sell = new int[n][k];
        Arrays.fill(buy[0], -prices[0]);
        for (int i = 1; i < n; ++i) {
            buy[i][0] = Math.max(buy[i - 1][0], -prices[i]);
            sell[i][0] = Math.max(sell[i - 1][0], buy[i - 1][0] + prices[i]);
            for (int j = 1; j < k; ++j) {
                buy[i][j] = Math.max(buy[i - 1][j], sell[i - 1][j - 1] - prices[i]);
                sell[i][j] = Math.max(sell[i - 1][j], buy[i - 1][j] + prices[i]);
            }
        }
        System.out.println(sell[n - 1][k - 1]);
    }
}

1058. 股票买卖 V（冷冻期）

https://www.acwing.com/problem/content/1060/
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限制 buy[i] 只能从 sell[i - 2] 转移过来就好了。

import java.io.BufferedInputStream;
import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sin = new Scanner(new BufferedInputStream(System.in));
        int n = sin.nextInt();
        int[] buy = new int[n], sell = new int[n], prices = new int[n];
        for (int i = 0; i < n; ++i) prices[i] = sin.nextInt();
        buy[0] = -prices[0];
        buy[1] = Math.max(buy[0], -prices[1]);
        sell[1] = Math.max(sell[0], buy[0] + prices[1]);
        for (int i = 2; i < n; ++i) {
            buy[i] = Math.max(sell[i - 2] - prices[i], buy[i - 1]);
            sell[i] = Math.max(buy[i - 1] + prices[i], sell[i - 1]);
        }
        System.out.println(sell[n - 1]);
    }
}