[Swust OJ 465]--吴奶奶买鱼(0-1背包+dfs)

 1 /******************0-1背包+dfs******************/
 2 #include <iostream>
 3 using namespace std;
 4 
 5 #define rep(i,a,b) for(int i=a;i<=b;i++)
 6 
 7 int buy[31], sign[31];//sign标记鱼的购买状态,buy最优购买方案
 8 int mpt[31][31];//表示鱼的相互克制状态
 9 int val, num, n, m, vi[31];//vi价格
10 
11 void dfs(int cur, int sum, int cnt){
12     int ptr[31];//中转变量
13     if (cur > n){
14         if (num<cnt || (num == cnt&&sum>val)){
15             num = cnt;
16             val = sum;
17             rep(i, 1, n)buy[i] = sign[i];
18         }
19         return;
20     }
21     if (!sign[cur] && sum + vi[cur] <= m){
22         rep(i, 1, n) ptr[i] = sign[i];
23         sign[cur] = 2;//标记这条鱼已购买
24         rep(i, 1, n){
25             if (mpt[cur][i] && !sign[i])
26                 sign[i] = 1;
27         }
28         dfs(cur + 1, sum + vi[cur], cnt + 1);
29         //还原鱼的购买状态，方便下一次搜索
30         rep(i, 1, n) sign[i] = ptr[i];
31         sign[cur] = 0;
32     }
33     dfs(cur + 1, sum, cnt);
34 }
35 int main(){
36     int a, b;
37     cin >> m >> n;
38     //鱼不一定按顺序给出,坑爹啊~~
39     rep(i, 1, n){
40         cin >> a;
41         cin >> vi[a];
42     }
43     cin >> a >> b;
44     while (a || b){
45         mpt[a][b] = mpt[b][a] = 1;
46         cin >> a >> b;
47     }
48     dfs(1, 0, 0);
49     cout << num << ‘ ‘ << val <<endl;
50     rep(i, 1, n){
51         if (buy[i] == 2)
52             cout << i << endl;
53     }
54     return 0;
55 }