2017 Multi-University Training Contest - Team 3 1005 RXD and dividing
2017-08-02 13:32
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题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=6060
题目大意: 给n个点和n-1条边, 每条边有个权值, 现在让你把2~n个点分到k个集合中, 每个点只能分到一个集合中, 在每个集合中的点和一号点形成一个最小生成树, 现在让你分这n个点, 使得k个几个的最小生成树的权值和最大。
解题思路: 对于一条边, 我们求出这条边下面的点数sz, 如果sz, 如果sz > k 这条边就会给答案贡献k次, 反之 贡献sz次。
//2017-08-02 13:02
//2017-08-02 13:29
#include<cstdio>
#include<cstring>
#include<cmath>
#include<cstdlib>
#include<queue>
#include<vector>
#include<algorithm>
using namespace std;
typedef long long LL;
typedef pair<int , int> PII;
const int MaxN = 1e6;
vector<PII> edge[MaxN + 5];
int sz[MaxN + 5], falen[MaxN + 5];
int n, k;
LL ans;
void dfs(int u, int fa, int l){
falen[u] = l;
sz[u]++;
for(int i = 0; i < edge[u].size(); i++){
int v = edge[u][i].first;
int nxtl = edge[u][i].second;
if(v != fa){
dfs(v, u, nxtl);
sz[u] += sz[v];
}
}
ans = ans + (LL)falen[u] * (LL)min(sz[u], k);
}
int main(){
while(~scanf("%d %d", &n, &k)){
ans = 0;
memset(sz, 0, sizeof(sz));
memset(falen, 0, sizeof(falen));
memset(edge, 0, sizeof(edge));
for(int i = 1; i < n; i++){
int u, v, c;
scanf("%d %d %d", &u, &v, &c);
edge[u].push_back(make_pair(v, c));
edge[v].push_back(make_pair(u, c));
}
dfs(1, 0, 0);
printf("%lld\n", ans);
}
return 0;
}
比赛的时候这道题没读懂, 也没怎么想, 结束之后听他们一讲题意才明白。
题目大意: 给n个点和n-1条边, 每条边有个权值, 现在让你把2~n个点分到k个集合中, 每个点只能分到一个集合中, 在每个集合中的点和一号点形成一个最小生成树, 现在让你分这n个点, 使得k个几个的最小生成树的权值和最大。
解题思路: 对于一条边, 我们求出这条边下面的点数sz, 如果sz, 如果sz > k 这条边就会给答案贡献k次, 反之 贡献sz次。
//2017-08-02 13:02
//2017-08-02 13:29
#include<cstdio>
#include<cstring>
#include<cmath>
#include<cstdlib>
#include<queue>
#include<vector>
#include<algorithm>
using namespace std;
typedef long long LL;
typedef pair<int , int> PII;
const int MaxN = 1e6;
vector<PII> edge[MaxN + 5];
int sz[MaxN + 5], falen[MaxN + 5];
int n, k;
LL ans;
void dfs(int u, int fa, int l){
falen[u] = l;
sz[u]++;
for(int i = 0; i < edge[u].size(); i++){
int v = edge[u][i].first;
int nxtl = edge[u][i].second;
if(v != fa){
dfs(v, u, nxtl);
sz[u] += sz[v];
}
}
ans = ans + (LL)falen[u] * (LL)min(sz[u], k);
}
int main(){
while(~scanf("%d %d", &n, &k)){
ans = 0;
memset(sz, 0, sizeof(sz));
memset(falen, 0, sizeof(falen));
memset(edge, 0, sizeof(edge));
for(int i = 1; i < n; i++){
int u, v, c;
scanf("%d %d %d", &u, &v, &c);
edge[u].push_back(make_pair(v, c));
edge[v].push_back(make_pair(u, c));
}
dfs(1, 0, 0);
printf("%lld\n", ans);
}
return 0;
}
比赛的时候这道题没读懂, 也没怎么想, 结束之后听他们一讲题意才明白。
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