Sightseeing Time Limit: 2000MS   Memory Limit: 65536K Total Submissions: 9247   Accepted: 3242 Description Tour operator Your Personal Holiday organises guided bus trips across the Benelux. Every day the bus moves from one city S to another city F. O…

传送门 用dijkstra比较好,spfa可能有的重复 dis[x][2]:dis[x][0]表示起点到x的最短路.dis[x][1]表示起点到x的次短路: tot[x][2]:tot[x][0]表示起点到x的最短路条数.tot[x][1]表示起点到x的次短路的条数: vis[x][2]对应于x和0.1功能为记录该点是否被访问! 那么如何更新最小和次小路呢?显然我们容易想到下面的方法: 1.if(x<最小)更新最小,次小:2.else if(x==最小)更新方法数:3.else if(x<次小…

题目:http://poj.org/problem?id=3463 次短路计数问题,在更新最短路的同时分类成比最短路短.长于最短路而短于次短路.比次短路长三种情况讨论一下,更新次短路: 然而其实不必被“同时”限制,否则就容易像我一开始一样写挂... 像拆点一样把最短路和次短路完全分开,放进 dijkstra 的优先队列里,真是巧妙: 还要注意一点是直接更新最短路之后要把它的次短路也加进优先队列里,因为次短路同时也被更新了. 代码如下: #include<iostream> #include&l…

题目大意:求两点间最短路与长度为最短路长度+1的路径的条数之和. 方法1:最短路径+DP 首先求出ST间最短路径,然后根据递归式记忆化搜索(因此还要构造反向图). 我们知道到达终点的路径长度最长为maxDist(T)=minDist(T)+1,而与终点相连的节点的路径长度最长为maxDist(T)-Weight(e).这些节点与更前面的节点也是如此.于是我们从终点开始递归,利用PathCnt(v)=sum(PathCnt(u)) (PathCnt(u)=|{Dist(u)|Dist(u)<=ma…

Sightseeing tour Time Limit: 1000MS   Memory Limit: 10000K Total Submissions: 9276   Accepted: 3924 Description The city executive board in Lund wants to construct a sightseeing tour by bus in Lund, so that tourists can see every corner of the beauti…

Sightseeing Cows Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 8331   Accepted: 2791 Description Farmer John has decided to reward his cows for their hard work by taking them on a tour of the big city! The cows must decide how best to…

Sightseeing tour Time Limit: 1000MS   Memory Limit: 10000K Total Submissions: 8859   Accepted: 3728 Description The city executive board in Lund wants to construct a sightseeing tour by bus in Lund, so that tourists can see every corner of the beauti…

Sightseeing tour Time Limit: 1000MS   Memory Limit: 10000K Total Submissions: 6986   Accepted: 2901 Description The city executive board in Lund wants to construct a sightseeing tour by bus in Lund, so that tourists can see every corner of the beauti…

Sightseeing tour   Description The city executive board in Lund wants to construct a sightseeing tour by bus in Lund, so that tourists can see every corner of the beautiful city. They want to construct the tour so that every street in the city is vis…

Sightseeing Time Limit: 3000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 1023    Accepted Submission(s): 444 Problem Description Tour operator Your Personal Holiday organises guided bus trips across the Ben…