Ural 1018 binary apple tree (tree DP)

Link: (-_-) ZZ

There is an apple tree. The Apple Tree is a binary tree with N nodes in total. The tree node number is 1 ~ N, the node numbered 1 is the root of the tree, and the edge can be understood as the branch of the tree. Each branch has several apples. Now we need to subtract several branches and keep M branches, the maximum number of apples in the M branch is required.

Idea: tree-like DP, DP [I] [J] indicates the number of apples with J edges when the root node is I. There are two cases for selecting the left subtree and the right subtree.

1: All J edges are on the left or right sub-number.

2: J lines of edge have left Tree and right tree together (now to discuss the situation, how many lines on the left, how many lines on the right, the left or the right of the maximum J-2, it should be the two from the root node to the two nodes)

PS: the first tree-like DP with claws

Code:

# Include <stdio. h> # include <string. h> # define max (A, B) A> B? A: bstruct {int L, R;} tree [102]; int n = 0, m = 0, map [102] [102], used [102], DP [102] [102]; void build_tree (INT c) {int I = 0, flag = 0; for (I = 1; I <= N; I ++) {If (Map [C] [I] &! Used [I]) {If (! Tree [C]. L) tree [C]. L = I, flag = 1, used [I] = 1; else if (! Tree [C]. r) // only the left and right vertices {tree [C]. R = I, flag = 1, used [I] = 1; break ;}} if (! Flag) return; build_tree (tree [C]. l); build_tree (tree [C]. r);} void dp (INT c) {int I = 0, j = 0, L = tree [C]. l, r = tree [C]. r; If (! Tree [C]. l) return; DP (tree [C]. l); DP (tree [C]. r); DP [C] [1] = max (Map [C] [L], map [C] [r]); // select the big side on the left or right of the current node for (I = 2; I <= m; I ++) {DP [C] [I] = max (DP [l] [I-1] + map [C] [L], DP [r] [I-1] + map [C] [r]); // select the left or right subtree for (j = 0; j <I-1; j ++) // select DP [C] [I] = max (DP [C] [I] for both left and right subtree. DP [l] [J] + dp [r] [i-j-2] + map [C] [l] + map [C] [r]); // The subtree on the left or right is a maximum of I-2 edges and should have two edges from the root node to the left and right nodes} int main () {int I = 0, u = 0, V = 0, cost = 0; while (scanf ("% d ", & N, & M )! = EOF) {memset (MAP, 0, sizeof (MAP); memset (used, 0, sizeof (used); memset (tree, 0, sizeof (tree )); memset (DP, 0, sizeof (DP); used [1] = 1; for (I = 1; I <n; I ++) {scanf ("% d", & U, & V, & cost); If (Map [u] [v] <cost) map [u] [v] = map [v] [u] = cost;} build_tree (1); DP (1); printf ("% d \ n ", DP [1] [m]);} return 0 ;}