[Swust OJ 360]--加分二叉树(区间dp)

 1 #include <iostream>
 2 #include <cstring>
 3 #include <cstdio>
 4 #include <algorithm>
 5 using namespace std;
 6 
 7 const int maxn = 50, inf = -0x7fffffff;
 8 int n,ptr, vi[maxn], dp[maxn][maxn], root[maxn][maxn];
 9 //若根节点的下标是k，则左端点的是k-1，右端点是k+1；
10 void PreOrder(int vi, int y){
11     if (root[vi][y]){
12         if (ptr++) cout << ‘ ‘;
13         cout << root[vi][y];
14         PreOrder(vi, root[vi][y] - 1);
15         PreOrder(root[vi][y] + 1, y);
16     }
17 }
18 
19 int main(){
20     //freopen("360-加分二叉树.in","r",stdin);
21     //freopen("360-加分二叉树.out", "w", stdout);
22     while (cin >> n){
23         for (int i = 0; i <= n; i++)
24         for (int j = 0; j <= n; j++)
25             dp[i][j] = 1;
26         for (int i = 1; i <= n; i++){
27             cin >> vi[i];
28             dp[i][i] = vi[i];
29             root[i][i] = i;
30         }
31         for (int r = 1; r <= n; r++){
32             for (int i = 1; i <= n - r; i++){
33                 int j = i + r, tmp = inf;
34                 for (int k = i; k < j; k++){
35                     if (tmp < (dp[i][k - 1] * dp[k + 1][j] + vi[k])){
36                         tmp = dp[i][k - 1] * dp[k + 1][j] + vi[k];
37                         root[i][j] = k;
38                     }
39                 }
40                 dp[i][j] = tmp;
41             }
42         }
43         cout << dp[1][n] << endl;
44         ptr = 0;
45         PreOrder(1, n);
46         cout << endl;
47     }
48     //fclose(stdin); fclose(stdout);
49     return 0;
50 }