传送门 很简单的一道题,被卡了几次,死于答案非法统计. 题意是求图里的一条最长的路径满足起点的入度和终点的出度都是0,而且图是DAG. 既然是DAG求最长路,DP即可.搞出拓扑序,逆序DP,然后统计所有入度为0的点的答案. //POJ 3249 //by Cydiater //2016.10.26 #include <iostream> #include <cstring> #include <string> #include <algorithm> #in…

link:http://poj.org/problem?id=3249 在拓扑排序的过程中进行状态转移,dp[i]表示从起点到 i 这个点所得到的的最大值.比如从u点到v点,dp[v]=max(dp[v], dp[u]+a[v])   a[]数组是点的价值,最终的dp[]数组里面的最大值就是所求的. #include <iostream> #include <cstdio> #include <cstdlib> #include <cstring> #inc…

显然是一道最短路径的题目,但是 1 ≤ n ≤ 100000, 0 ≤ m ≤ 1000000能轻松打爆dij+heap 怎么办? 挖掘题意,这是一个DAG图(有向无环图) 所以对于此类问题,我们有特殊的作法 对于DAG,拓扑序列在前的点的最短路一定会被先更新(值得思考) 所以我们只用对DAG做一次拓扑,然后依次更新最短路即可:(其实很像dp) 多个入度为0的点不影响结果: 再回到这题,由于给出的是点的权值 可以考虑拆点,将点i拆成点i1,i2,i1,i2之间连一条指向i2的有向边,权值为原先点…

题意:给出一个有向无环图,每个顶点都有一个权值.求一条从入度为0的顶点到出度为0的顶点的一条路径,路径上所有顶点权值和最大. 思路:因为是无环图,则对于每个点经过的路径求其最大权值有,dp[i]=max(dp[j])  j为i的子节点集合.再根据其要求入度为零为顶点,可以用拓扑排序每次枚举入度为零的点删去找下一个入度为零的点进行dp. 代码: #include <cstdio> #include <cstring> #include <iostream> using n…

Test for Job Time Limit: 5000MS   Memory Limit: 65536K Total Submissions: 10567   Accepted: 2482 Description Mr.Dog was fired by his company. In order to support his family, he must find a new job as soon as possible. Nowadays, It's hard to have a jo…

//题意:   给出一个有向无环图,每个顶点都有一个权值. //         求一条从入度为0的顶点到出度为0的顶点的一条路径, //         路径上所有顶点权值和最大. //我觉得只要明白 //图论里的链式前向星   的  建图原理  和  拓扑排序的一点知识就完全有能力打出来 //以后还是可以练练手的  所以写一发吧 //拓扑排序+优化一下 //author keyboarder //time   2016/4/23 21:52 #include <iostream> #inc…

Test for Job Time Limit: 5000MS   Memory Limit: 65536K Total Submissions: 10137   Accepted: 2348 Description Mr.Dog was fired by his company. In order to support his family, he must find a new job as soon as possible. Nowadays, It's hard to have a jo…

#include <cstdio> #include <cstdlib> #include <iostream> #include <algorithm> #include <cstring> #include <cmath> #include <stack> #include <vector> using namespace std; const int MAX=111111; int N,E; int v[…

Test for Job Time Limit: 5000MS   Memory Limit: 65536K Total Submissions: 11230   Accepted: 2651 Description Mr.Dog was fired by his company. In order to support his family, he must find a new job as soon as possible. Nowadays, It's hard to have a jo…

Test for Job Time Limit: 5000MS   Memory Limit: 65536K Total Submissions: 10209   Accepted: 2372 Description Mr.Dog was fired by his company. In order to support his family, he must find a new job as soon as possible. Nowadays, It's hard to have a jo…