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ioi05_rivers.cpp
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ioi05_rivers.cpp
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#include <cstdio>
#include <vector>
#include <utility>
#include <algorithm>
#include <cstring>
using namespace std;
typedef pair<int,int> pi;
vector<pi> graph[101];
int n,k,w[101],p[101];
int dist[101];
int dp[101][101][51];
void dfs(int x, int d){
dist[x] = d;
for (int i=0; i<graph[x].size(); i++) {
dfs(graph[x][i].second,d+graph[x][i].first);
}
}
int f(int x, int csub, int nearest, int left){
if(graph[x].size() == csub){
if(csub == 0){
if(left == 1) return 0;
else if(left == 0) return w[x] * (dist[x] - dist[nearest]);
return 1e9;
}
else return left ? 1e9 : 0;
}
if(~dp[graph[x][csub].second][nearest][left]) return dp[graph[x][csub].second][nearest][left];
int ret = 1e9;
if(csub == 0){
for (int i=0; i<left; i++) {
ret = min(ret,f(graph[x][csub].second,0,x,i) + f(x,csub+1,x,left-i-1));
}
for (int i=0; i<=left; i++) {
ret = min(ret,f(graph[x][csub].second,0,nearest,i) + f(x,csub+1,nearest,left-i) + w[x] * (dist[x] - dist[nearest]));
}
}
else{
for (int i=0; i<=left; i++) {
ret = min(ret,f(graph[x][csub].second,0,nearest,i) + f(x,csub+1,nearest,left-i));
}
}
return dp[graph[x][csub].second][nearest][left] = ret;
}
int main(){
memset(dp,-1,sizeof(dp));
scanf("%d %d",&n,&k);
for (int i=1; i<=n; i++) {
int q;
scanf("%d %d %d",&w[i],&p[i],&q);
graph[p[i]].push_back(pi(q,i));
}
dfs(0,0);
printf("%d",f(0,0,0,k));
}