POJ 3411 Paid Roads Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 6553   Accepted: 2430 Description A network of m roads connects N cities (numbered from 1 to N). There may be more than one road connecting one city with another. Some o…

Description A network of m roads connects N cities (numbered to N). There may be more than one road connecting one city with another. Some of the roads are paid. There are two ways to pay for travel on a paid road i from city ai to city bi: in advanc…

题意:给你N 城市和M条道路,每条道路要付的钱,但是如果你在这个道路上你可以付其他道路的钱(跟走到的时候去的话不一样),问你从1走到N最少话费是多少. 直接DFS搜. 链接http://poj.org/problem?id=3411 代码: #include <stdio.h> #include <string.h> #include <iostream> #include <algorithm> #include <stdlib.h> #inc…

题目链接 点和边 都很少,确定一个界限,爆搜即可.判断点到达注意一下,如果之前已经到了,就不用回溯了,如果之前没到过,要回溯. #include <cstring> #include <cstdio> #include <string> #include <iostream> #include <algorithm> #include <vector> #include <queue> using namespace st…

题目链接 题意 : 要从1城市到n城市,求最短路是多少,从a城市到达b城市的路程,如果你到过c城市,则需要走p,否则走r长. 思路 : 因为可以来回走,所以不能用单纯的最短路,可以用二维SPFA,状态压缩一下,第二维来记录状态,表示到过这个点的第几个状态.也可以用DFS,因为最多十个点,所以如果走某一个点走过三遍说明就是真的只增加费用了,也就是真正的在走环路了.DFS分析 二维SPFA #include <stdio.h> #include <string.h> #include…

题意:有m条路,n座城市,走这些路是要付费的,每条路由两种付费方案,设一条路两端是a,b,如果走完这条路在b点付费的话,应付r,如果走这条路之前在c点付费的话,应付p,求从1端点走到n端点的最小费用. DFS 刚开始想到了用搜索,自己搜索学的不好,有几个问题解决不了,首先就是每个点可以走多次,不能用0,1标记一个点是否走过,如果不标记就可能在一直走一条循环路,还有就是不会回溯,总之,自己就是不会写... 网上抄的别人的代码,每个点最多可以走3次,回溯也挺简单... #include<stdio.…

题意:有n座城市和m(1<=n,m<=10)条路.现在要从城市1到城市n.有些路是要收费的,从a城市到b城市,如果之前到过c城市,那么只要付P的钱, 如果没有去过就付R的钱.求的是最少要花多少钱. 析:BFS,然后由于走的路线不同,甚至边或者点都可能多走,所以用状态压缩.然后本题有坑啊,有重连,而且有很多条重边,所以多走几次就好了. 代码如下: #pragma comment(linker, "/STACK:1024000000,1024000000") #include…

poj   1251  Jungle Roads  (最小生成树) Link: http://poj.org/problem?id=1251 Jungle Roads Time Limit: 1000MS   Memory Limit: 10000K Total Submissions: 23507   Accepted: 11012 Description The Head Elder of the tropical island of Lagrishan has a problem. A b…

HDU 1815, POJ 2749 Building roads pid=1815" target="_blank" style="">题目链接HDU 题目链接POJ 题意: 有n个牛棚, 还有两个中转站S1和S2, S1和S2用一条路连接起来. 为了使得随意牛棚两个都能够有道路联通,如今要让每一个牛棚都连接一条路到S1或者S2. 有a对牛棚互相有仇恨,所以不能让他们的路连接到同一个中转站. 还有b对牛棚互相喜欢,所以他们的路必须连到同一个中专站.…

[题解]Paid Roads [SP3953] [Poj3411] 传送门:\(\text{Paid}\) \(\text{Roads}\) \(\text{[SP3953]}\) \(\text{[Poj3411]}\) [题目描述] 给出一张 \(n\) 个点 \(m\) 条边的有向图.对于每条边 \((x,y)\),如果之前经过 \(z\) 点,那么费用为 \(p\),否则为 \(r\).求 \(1\) 到 \(n\) 的最小费用.如果无法到达则输出 " \(\text{impossibl…

题目链接:http://poj.org/problem?id=3411 题目意思:N个city 由 m 条路连接,对于一条路(假设连接Cityia和 Cityb),如果从Citya 去 Cityb的途中,之前已经走过Cityc(可能会等于a),那么就可以交p的钱,否则之前未走过Cityc,就一定要交r 的路费啦. 注意,一个点可以被反复多次走,也就是可能构成环,虽然路走长了,但路费便宜了,这个问题要考虑到.还有就是剪枝啦:如果当前求得的路费比以前求得的答案要大,那就要回溯. mincost 明明…

A network of m roads connects N cities (numbered from 1 to N). There may be more than one road connecting one city with another. Some of the roads are paid. There are two ways to pay for travel on a paid road i from city ai to city bi: in advance, in…

ROADS Time Limit: 1000MS Memory Limit: 65536K Total Submissions: 12436 Accepted: 4591 Description N cities named with numbers 1 - N are connected with one-way roads. Each road has two parameters associated with it : the road length and the toll that…

D - Jungle Roads Time Limit:1000MS     Memory Limit:10000KB     64bit IO Format:%I64d & %I64u Submit Status Practice POJ 1251 Description The Head Elder of the tropical island of Lagrishan has a problem. A burst of foreign aid money was spent on extr…

题目连接 http://poj.org/problem?id=3625 Building Roads Description Farmer John had just acquired several new farms! He wants to connect the farms with roads so that he can travel from any farm to any other farm via a sequence of roads; roads already conn…

Constructing Roads Time Limit:2000MS     Memory Limit:65536KB     64bit IO Format:%I64d & %I64u Submit Status Practice POJ 2421 Appoint description:  System Crawler  (2015-05-27) Description There are N villages, which are numbered from 1 to N, and y…

Building roads Time Limit: 2000MS   Memory Limit: 65536K Total Submissions: 6229   Accepted: 2093 Description Farmer John's farm has N barns, and there are some cows that live in each barn. The cows like to drop around, so John wants to build some ro…

Rebuilding Roads Time Limit: 1000MS Memory Limit: 30000K Total Submissions: 10653 Accepted: 4884 Description The cows have reconstructed Farmer John's farm, with its N barns (1 <= N <= 150, number 1..N) after the terrible earthquake last May. The co…

http://poj.org/problem?id=2421 Time Limit: 2000MS   Memory Limit: 65536K Total Submissions: 24132   Accepted: 10368 Description There are N villages, which are numbered from 1 to N, and you should build some roads such that every two villages can con…

Description The Head Elder of the tropical island of Lagrishan has a problem. A burst of foreign aid money was spent on extra roads between villages some years ago. But the jungle overtakes roads relentlessly, so the large road network is too expensi…

树形DP..... Rebuilding Roads Time Limit: 1000MS Memory Limit: 30000K Total Submissions: 8188 Accepted: 3659 Description The cows have reconstructed Farmer John's farm, with its N barns (1 <= N <= 150, number 1..N) after the terrible earthquake last Ma…

Rebuilding Roads   Description The cows have reconstructed Farmer John's farm, with its N barns (1 <= N <= 150, number 1..N) after the terrible earthquake last May. The cows didn't have time to rebuild any extra roads, so now there is exactly one wa…

题目链接:http://poj.org/problem?id=2421 实际上又是考最小生成树的内容,也是用到kruskal算法.但稍稍有点不同的是,给出一些已连接的边,要在这些边存在的情况下,拓展出最小生成树来. 一般来说,过到这四组数据大体上就能AC了.  1.题目给出的案例数据    2.连接的道路可能把所有的村庄都已经连通了       3.两个村庄给出多次,即连接这两个村庄的道路是重复的!. 2.3这两种情况的数据如下(为了好看,自己出了一组,当然Sample Input 那组也行):…

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个节点最少减去的边数. 考虑两种情况,去掉孩子节点v与去不掉. (1)去掉孩子节点:dp[u][j] = dp[u][j] + 1 (2)不去掉孩子节点:dp[u][j] = min(dp[u][j - k] + dp[v][k]) 综上就是dp[u][j] = min(dp[u][j] + 1, min(dp[…

Constructing Roads 题目链接: http://acm.hust.edu.cn/vjudge/contest/124434#problem/D Description There are N villages, which are numbered from 1 to N, and you should build some roads such that every two villages can connect to each other. We say two villa…

题意  有n个村子  输入n  然后n-1行先输入村子的序号和与该村子相连的村子数t  后面依次输入t组s和tt s为村子序号 tt为与当前村子的距离  求链接全部村子的最短路径 还是裸的最小生成树咯 #include<cstdio> #include<cstring> #include<algorithm> using namespace std; const int N=30,M=1000; int par[N],n,m,ans; struct edge{int u…

题目: Description The Head Elder of the tropical island of Lagrishan has a problem. A burst of foreign aid money was spent on extra roads between villages some years ago. But the jungle overtakes roads relentlessly, so the large road network is too exp…

Constructing Roads Description There are N villages, which are numbered from 1 to N, and you should build some roads such that every two villages can connect to each other. We say two village A and B are connected, if and only if there is a road betw…

Rebuilding Roads Time Limit: 1000MS   Memory Limit: 30000K Total Submissions: 9105   Accepted: 4122 Description The cows have reconstructed Farmer John's farm, with its N barns (1 <= N <= 150, number 1..N) after the terrible earthquake last May. The…

题目: The Head Elder of the tropical island of Lagrishan has a problem. A burst of foreign aid money was spent on extra roads between villages some years ago. But the jungle overtakes roads relentlessly, so the large road network is too expensive to ma…