幸运的袋子（深度优先遍历）

 1 /**
 2  * 幸运的袋子
 3       1、对于a+b>a*b 必然有 一个数为1
 4  * @author Dell
 5  *
 6  */
 7 
 8 import java.util.ArrayList;
 9 import java.util.Arrays;
10 import java.util.HashSet;
11 import java.util.List;
12 import java.util.Scanner;
13 import java.util.Set;
14 
15 public class Main {
16 
17     static public int dfs(int a[], int index, long sum, long multi) {
18         int count = 0;
19         for (int i = index; i < a.length; i++) {
20             sum += a[i];
21             multi *= a[i];
22 
23             if (sum > multi) {// 目前幸运接着递归
24                 count = count + 1 + dfs(a, i + 1, sum, multi);
25             } else if (a[i] == 1) { // a[i] = 1  还有机会
26                 count = count + dfs(a, i + 1, sum, multi);
27             } else {// 不幸运  退出
28                 break;
29             }
30 
31             sum -= a[i];
32             multi /= a[i];
33             for (; i < a.length - 1 && a[i] == a[i + 1]; i++) {
34                 // 相同号码 球取哪个 无区别 跳过
35             }
36         }
37         return count;
38     }
39     public static void main(String[] args) {
40         Scanner sc =new Scanner(System.in);
41         while(sc.hasNext()) {
42             int n = sc.nextInt();
43             int []a = new int[n];
44             for (int i = 0; i < a.length; i++) {
45                 a[i] = sc.nextInt();
46             }
47             Arrays.sort(a);
48             System.out.println(dfs(a,0,0,1));
49         }
50     }
51 
52 }