动态规划实现钢条切割问题

 1 /**
 2  * 动态规划实现实现钢条切割问题
 3  */
 4 public class Test1 {
 5 
 6     static int[] result = {0,0,0,0,0,0,0,0,0,0,0};
 7     static int[] s = {0,0,0,0,0,0,0,0,0,0,0};
 8     
 9     public static void main(String[] args) {
10         int[] arr = {0,1,5,8,9,10,17,17,20,24,30};
11         /*
12         System.out.println("自顶向下结果");
13         for (int i = 0; i < arr.length; i++) {
14             System.out.print("r"+ i +"=" + UpDown(i, arr)+"; ");
15         }
16         */
17         /*
18         System.out.println("自底向上结果");
19         for (int i = 0; i < arr.length; i++) {
20             System.out.print("r"+ i +"=" + DownUp(i, arr)+"; ");
21         }
22         */
23     }
24     
25     /**
26      * 自顶向下实现
27      */
28     static int UpDown(int num, int[] arr) {
29         if(num == 0) return 0;
30         if(result[num] != 0) return result[num];
31         
32         int temp = 0;
33         for (int i = 1; i < num+1; i++) {
34             int max = arr[i] + UpDown(num-i, arr);
35             if(max > temp) {
36                 temp = max;
37             }
38         }
39         result[num] = temp; //将计算的长度为n的钢条切割的长度用数组保存起来
40         return temp;
41     }
42     
43     /**
44      * 自底向上实现
45      */
46     static int DownUp(int num, int[] arr) {
47         for (int i = 1; i < num + 1; i++) {
48             int temp = 0;
49             for (int j = 1; j <= i; j++) {
50                 int max = arr[j] + result[i - j];
51                 if(max > temp) {
52                     temp = max;
53                 }
54             }
55             result[i] = temp;
56         }
57         return result[num];
58     }
59 }