Tree Pruning
Problem Statement :
A tree, t, has n vertices numbered from 1 to n and is rooted at vertex 1. Each vertex i has an integer weight, wi, associated with it, and t's total weight is the sum of the weights of its nodes. A single remove operation removes the subtree rooted at some arbitrary vertex u from tree t. Given t, perform up to k remove operations so that the total weight of the remaining vertices in t is maximal. Then print t's maximal total weight on a new line. Note: If t's total weight is already maximal, you may opt to remove 0 nodes. Input Format The first line contains two space-separated integers, n and k, respectively. The second line contains n space-separated integers describing the respective weights for each node in the tree, where the ith integer is the weight of the ith vertex. Each of the n-1 subsequent lines contains a pair of space-separated integers, u and v, describing an edge connecting vertex u to vertex v. Constraints 2 <= n <= 10^5 1 <= k <= 200 1 <= i <=n -10^9 <= wi <= 10^9 Output Format Print a single integer denoting the largest total weight of t's remaining vertices.
Solution :
Solution in C :
In C++ :
#include <fstream>
#include <iostream>
#include <vector>
#include <bitset>
using namespace std;
const int NMAX = 100004;
const long long INF = 1LL<<60;
vector <int> Tree[NMAX], Level[NMAX];
long long dp[NMAX][201], sum[NMAX];
int n, Father[NMAX], v[NMAX], val[NMAX], First[NMAX], Last[NMAX], ind;
inline void DFS(const int node,const int father){
First[node] = ++ind;
v[ind] = node;
for(vector < int >::iterator it = Tree[node].begin();it != Tree[node].end();++it)
if(*it != father)
DFS(*it,node);
Last[node] = ind;
}
int main(){
int n, k;
cin.sync_with_stdio(false);
cin >> n >> k;
for(int i = 1;i <= n; ++i)
cin >> val[i];
for(int i=1;i<n;++i){
int x,y;
cin >> x >> y;
Tree[x].push_back(y);
Tree[y].push_back(x);
}
DFS(1,0);
for(int i = 1;i <= n; ++i){
for(int j=0;j<=k;++j)
dp[i][j] = -INF;
}
dp[1][0] = 0;
for(int i = 1;i <= n; ++i)
{
int node = v[i];
for(int j = 0;j <= k; ++j)
if(dp[i][j]!=-INF)
{
dp[i + 1][j] =max(dp[i+1][j],dp[i][j]+val[node]);
if(j+1<=k)
dp[Last[node]+1][j+1] = max(dp[i][j],dp[Last[node]+1][j+1]);
}
}
long long sol = 0;
for(int j = 0;j <= k;++j)
sol = max(sol,dp[n+1][j]);
cout<<sol<<"\n";
return 0;
}
In Java :
import java.util.List;
import java.io.IOException;
import java.util.Arrays;
import java.util.InputMismatchException;
import java.util.ArrayList;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.InputStream;
/**
* Built using CHelper plug-in
* Actual solution is at the top
*/
public class Solution {
public static void main(String[] args) {
InputStream inputStream = System.in;
OutputStream outputStream = System.out;
InputReader in = new InputReader(inputStream);
PrintWriter out = new PrintWriter(outputStream);
TreePruning solver = new TreePruning();
solver.solve(1, in, out);
out.close();
}
}
class TreePruning {
int[] w;
List<Integer>[] t;
List<Integer>[] dt;
int[] cnt;
long[][] dp;
int k;
public void solve(int testNumber, InputReader in, PrintWriter out) {
int n = in.nextInt();
k = in.nextInt();
dp = new long[n][];
w = new int[n];
t = new List[n];
dt = new List[n];
cnt = new int[n];
for (int i = 0; i < n; i++) {
w[i] = in.nextInt();
t[i] = new ArrayList<>();
dt[i] = new ArrayList<>();
}
for (int i = 0; i < n - 1; i++) {
int u = in.nextInt() - 1;
int v = in.nextInt() - 1;
t[u].add(v);
t[v].add(u);
}
prepare(0, -1);
dfs(0);
long res = Long.MIN_VALUE;
for (int i = 0; i < dp[0].length; i++) {
res = Math.max(res, dp[0][i]);
}
out.println(res);
}
void dfs(int u) {
for (int v : dt[u]) {
dfs(v);
}
long[] d = new long[Math.min(cnt[u], k) + 1];
for (int v : dt[u]) {
long[] nd = new long[d.length];
Arrays.fill(nd, Long.MIN_VALUE / 2);
for (int i = 0; i < d.length; i++) {
for (int j = 0; j < dp[v].length && i + j < nd.length; j++) {
nd[i + j] = Math.max(nd[i + j], d[i] + dp[v][j]);
}
}
d = nd;
}
for (int i = 0; i < d.length; i++) {
d[i] += w[u];
}
if (d.length > 0)
d[1] = Math.max(d[1], 0);
dp[u] = d;
}
void prepare(int u, int p) {
if (p != -1) {
dt[p].add(u);
}
cnt[u] = 1;
for (int v : t[u]) {
if (v != p) {
prepare(v, u);
cnt[u] += cnt[v];
}
}
}
}
class InputReader {
final InputStream is;
final byte[] buf = new byte[1024];
int pos;
int size;
public InputReader(InputStream is) {
this.is = is;
}
public int nextInt() {
int c = read();
while (isWhitespace(c))
c = read();
int sign = 1;
if (c == '-') {
sign = -1;
c = read();
}
int res = 0;
do {
if (c < '0' || c > '9')
throw new InputMismatchException();
res = res * 10 + c - '0';
c = read();
} while (!isWhitespace(c));
return res * sign;
}
int read() {
if (size == -1)
throw new InputMismatchException();
if (pos >= size) {
pos = 0;
try {
size = is.read(buf);
} catch (IOException e) {
throw new InputMismatchException();
}
if (size <= 0)
return -1;
}
return buf[pos++] & 255;
}
static boolean isWhitespace(int c) {
return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
}
}
In C :
#include <stdio.h>
#include <stdlib.h>
typedef struct _node{
int x;
struct _node *next;
} node;
void insert_edge(int x,int y);
void dfs(int x);
long long max(long long x,long long y);
int a[100000],b[100000],size[100000],trace[100000]={0},NN=0;
long long dp[100001][201];
node *table[100000]={0};
int main(){
int N,K,x,y,i,j;
long long sum;
scanf("%d%d",&N,&K);
for(i=0;i<N;i++)
scanf("%d",a+i);
for(i=0;i<N-1;i++){
scanf("%d%d",&x,&y);
insert_edge(x-1,y-1);
}
dfs(0);
for(i=0;i<=K;i++)
dp[0][i]=0;
for(i=1,sum=0;i<=N;i++){
sum+=b[i-1];
for(j=0;j<=K;j++)
dp[i][j]=sum;
}
for(i=1,sum=0;i<=N;i++)
for(j=0;j<=K;j++){
if(j!=K)
dp[i+size[i-1]-1][j+1]=max(dp[i+size[i-1]-1][j+1],dp[i-1][j]);
dp[i][j]=max(dp[i][j],dp[i-1][j]+b[i-1]);
}
printf("%lld",dp[N][K]);
return 0;
}
void insert_edge(int x,int y){
node *t;
t=(node*)malloc(sizeof(node));
t->x=y;
t->next=table[x];
table[x]=t;
t=(node*)malloc(sizeof(node));
t->x=x;
t->next=table[y];
table[y]=t;
return;
}
void dfs(int x){
node *t;
int i=NN;
trace[x]=1;
b[NN++]=a[x];
for(t=table[x];t;t=t->next)
if(!trace[t->x])
dfs(t->x);
size[i]=NN-i;
return;
}
long long max(long long x,long long y){
return (x>y)?x:y;
}
In Python3 :
#!/bin/python3
import os
import sys
#
# Complete the treePrunning function below.
#
from collections import defaultdict
INF = -(1e15)
def dfs(x, f, g, k, weights):
dpc = [INF]*(k+1)
dpc[0] = weights[x]
for n in g[x]:
if n == f:
continue
dpn = dfs(n, x, g, k, weights)
dptmp = [INF]*(k+1)
for i in range(k+1):
if dpc[i] == INF:
break
for j in range(0, k-i+1):
if dpn[j] == INF:
break
dptmp[i+j] = max(dptmp[i+j], dpc[i]+dpn[j])
if i+1 <= k:
dptmp[i+1] = max(dptmp[i+1], dpc[i])
dpc = dptmp
return dpc
def treePrunning(k,weights,edges):
g = defaultdict(list)
for u, v in edges:
g[u-1].append(v-1)
g[v-1].append(u-1)
dpn = dfs(0, -1, g, k, weights)
return max(max(dpn),0)
if __name__ == '__main__':
fptr = open(os.environ['OUTPUT_PATH'], 'w')
nk = input().split()
n = int(nk[0])
k = int(nk[1])
weights = list(map(int, input().rstrip().split()))
tree = []
for _ in range(n-1):
tree.append(list(map(int, input().rstrip().split())))
result = treePrunning(k, weights, tree)
fptr.write(str(result) + '\n')
fptr.close()
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