POJ题目1947 Rebuilding Roads(树形dp)
Time Limit: 1000MS | Memory Limit: 30000K | |
Total Submissions: 9957 | Accepted: 4537 |
Description
barn. Thus, the farm transportation system can be represented as a tree.
Farmer John wants to know how much damage another earthquake could do. He wants to know the minimum number of roads whose destruction would isolate a subtree of exactly P (1 <= P <= N) barns from the rest of the barns.
Input
* Lines 2..N: N-1 lines, each with two integers I and J. Node I is node J's parent in the tree of roads.
Output
Sample Input
11 6
1 2
1 3
1 4
1 5
2 6
2 7
2 8
4 9
4 10
4 11
Sample Output
2
Hint
Source
题目大意:问一个数删掉最少条边变成一个仅仅有n个结点的子树
ac代码
#include<stdio.h>
#include<string.h>
#define min(a,b) (a>b? b:a)
#define INF 0xfffffff
int dp[220][220];
int pre[220],head[220],vis[220],dig[220];
int n,p,cnt;
struct s
{
int u,v,w,next;
}edge[220*2];
void add(int u,int v)
{
edge[cnt].u=u;
edge[cnt].v=v;
edge[cnt].next=head[u];
head[u]=cnt++;
}
void tree_dp(int u)
{
int i,j,k;
for(i=0;i<=p;i++)
{
dp[u][i]=INF;
}
dp[u][1]=0;
for(i=head[u];i!=-1;i=edge[i].next)
{
int v=edge[i].v;
tree_dp(v);
for(k=p;k>=1;k--)
{
dp[u][k]=dp[u][k]+1;
for(j=1;j<k;j++)
{ dp[u][k]=min(dp[u][k],dp[u][j]+dp[v][k-j]);
}
}
}
}
int DP(int u)
{
tree_dp(u);
int ans=dp[u][p];
int i;
for(i=1;i<=n;i++)
{
ans=min(ans,dp[i][p]+1);
// printf("%d\n",dp[i][1]);
}
return ans;
}
int main()
{
//int n,p;
while(scanf("%d%d",&n,&p)!=EOF)
{
int i;
memset(dig,0,sizeof(dig));
memset(head,-1,sizeof(head));
cnt=0;
for(i=0;i<n-1;i++)
{
int a,b;
scanf("%d%d",&a,&b);
add(a,b);
dig[b]++;
}
int root;
for(i=1;i<=n;i++)
{
if(dig[i]==0)
root=i;
}
printf("%d\n",DP(root));
}
}
POJ题目1947 Rebuilding Roads(树形dp)的更多相关文章
- POJ 1947 Rebuilding Roads 树形DP
Rebuilding Roads Description The cows have reconstructed Farmer John's farm, with its N barns (1 & ...
- POJ 1947 Rebuilding Roads 树形dp 难度:2
Rebuilding Roads Time Limit: 1000MS Memory Limit: 30000K Total Submissions: 9105 Accepted: 4122 ...
- DP Intro - poj 1947 Rebuilding Roads(树形DP)
版权声明:本文为博主原创文章,未经博主允许不得转载. Rebuilding Roads Time Limit: 1000MS Memory Limit: 30000K Total Submissi ...
- [poj 1947] Rebuilding Roads 树形DP
Rebuilding Roads Time Limit: 1000MS Memory Limit: 30000K Total Submissions: 10653 Accepted: 4884 Des ...
- POJ 1947 Rebuilding Road(树形DP)
Description The cows have reconstructed Farmer John's farm, with its N barns (1 <= N <= 150, n ...
- POJ1947 - Rebuilding Roads(树形DP)
题目大意 给定一棵n个结点的树,问最少需要删除多少条边使得某棵子树的结点个数为p 题解 很经典的树形DP~~~直接上方程吧 dp[u][j]=min(dp[u][j],dp[u][j-k]+dp[v] ...
- POJ 1947 Rebuilding Roads (树dp + 背包思想)
题目链接:http://poj.org/problem?id=1947 一共有n个节点,要求减去最少的边,行号剩下p个节点.问你去掉的最少边数. dp[u][j]表示u为子树根,且得到j个节点最少减去 ...
- 树形dp(poj 1947 Rebuilding Roads )
题意: 有n个点组成一棵树,问至少要删除多少条边才能获得一棵有p个结点的子树? 思路: 设dp[i][k]为以i为根,生成节点数为k的子树,所需剪掉的边数. dp[i][1] = total(i.so ...
- POJ 1947 Rebuilding Roads
树形DP..... Rebuilding Roads Time Limit: 1000MS Memory Limit: 30000K Total Submissions: 8188 Accepted: ...
随机推荐
- HDU 5279 分治NTT 图的计数
思路: 显然每个子图内都是森林 去掉所有子图1和n都连通且每条大边都存在的情况 直接DP上 NTT优化一波 注意前两项的值.. //By SiriusRen #include <bits/std ...
- SCOI2014总结
似乎还没有写过SCOI的总结,今天补上,权当填坑. PS:CDQZ的看到了不要到处黑 SCOI-2014应该算是我的小高考,感觉拿住一本招的瓶颈就在这里.加之NOIp只有400分有点拖后腿,所以很早就 ...
- Unicode gbk gb2312 编码问题 [转载]
原文地址: http://www.cnblogs.com/csn0721/archive/2013/01/24/2875613.html HTML5 UTF-8 中文乱码 <!DOCTYPE ...
- SharePoint通过IP地址访问
问题:SP站点通过计算机名称可以访问,但不能通过IP地址访问 解决方案:打开SharePoint2010管理中心>应用程序管理>配置备用访问映射>编辑公用 URL 备用访问映射集:选 ...
- 搭建本地wordpress
1.首先,下载xampp,安装按默认勾选即可. 2.安装完成后,启动Apache和MySQL这两个服务. 启动后变成绿色,表示启动成功. 3.点击MySQL项的Admin进入数据库后台. 4.点击用户 ...
- 3分钟看懂flex布局
首先要有个容器,并设置display:flex;display:-webkit-flex;该容器有以下六个属性: 1 2 3 4 5 6 7 8 9 10 11 12 flex-direction ( ...
- 如何学习Unity3D
如何学习 第一步首先了解unity3d的菜单,视图界面.这些事最基本的基础,可以像学word操作一样,大致能明白有几个菜单,几个基本的视图,各自起什么作用的就可以了. 第二步理解场景里面的坐标系统 ...
- linux共享库的版本控制
前几天看到一篇介绍linux共享库版本控制及使用的文章,觉得不错,这里就与大家分享一下. 1. Linux约定 经常看到Linux中,共享库的名字后面跟了一串数字,比如:libperl.so.5.18 ...
- Linux Shell 小知识
${} ——变量替换 通常 $var 与 ${var} 没有区别,但是用 ${} 会比较精确的界定变量名称的范围. name='Ace' echo "result1: my name is ...
- PHP控制反转(IOC)和依赖注入(DI
<?php class A { public $b; public $c; public function A() { //TODO } public function Method() { $ ...