3538: [Usaco2014 Open]Dueling GPS Time Limit: 1 Sec  Memory Limit: 128 MBSubmit: 59  Solved: 36[Submit][Status] Description Farmer John has recently purchased a new car online, but in his haste he accidentally clicked the "Submit" button twice w…

http://www.lydsy.com/JudgeOnline/problem.php?id=3538 题意不要理解错QAQ,是说当前边(u,v)且u到n的最短距离中包含这条边,那么这条边就不警告. 那么我们反向spfa两次,然后再正向spfa就行了 #include <cstdio> #include <cstring> #include <cmath> #include <string> #include <iostream> #inclu…

P3106 [USACO14OPEN]GPS的决斗Dueling GPS's 题目描述 Farmer John has recently purchased a new car online, but in his haste he accidentally clicked the "Submit" button twice when selecting extra features for the car, and as a result the car ended up equip…

洛谷 P3106 [USACO14OPEN]GPS的决斗Dueling GPS's 洛谷传送门 JDOJ 2424: USACO 2014 Open Silver 2.Dueling GPSs JDOJ传送门 Description Problem 2: Dueling GPS's [Brian Dean, 2014] Farmer John has recently purchased a new car online, but in his haste he accidentally cli…

P3106 [USACO14OPEN]GPS的决斗Dueling GPS's 题意 题目描述 Farmer John has recently purchased a new car online, but in his haste he accidentally clicked the "Submit" button twice when selecting extra features for the car, and as a result the car ended up eq…

题目描述 Farmer John has recently purchased a new car online, but in his haste he accidentally clicked the "Submit" button twice when selecting extra features for the car, and as a result the car ended up equipped with two GPS navigation systems! Ev…

[题解] 这两道题是完全一样的. 思路其实很简单,对于两种边权分别建反向图跑dijkstra. 如果某条边在某一种边权的图中不是最短路上的边,就把它的cnt加上1.(这样每条边的cnt是0或1或2,代表经过这条边GPS报警的次数) 最后用每条边的cnt作为边权建图,跑dijkstra即可. 判断某条边是不是最短路上的边:建反向图,以n为起点跑dijkstra,如果某条边(u,v)满足dis[v]=dis[u]+w,那么这条边是u到n的最短路上的边. #include<cstdio> #incl…

题目概况 题目描述 给你一个\(N\)个点的有向图,可能有重边. 有两个\(GPS\)定位系统,分别认为经过边\(i\)的时间为\(P_i\),和\(Q_i\). 每走一条边的时候,如果一个系统认为走的这条边不是它认为的最短路,就会受到警告一次. 两个系统是分开警告的,就是说当走的这条边都不在两个系统认为的最短路范围内,就会受到2次警告. 如果边\((u,v)\)不在\(u\)到\(n\)的最短路径上,这条边就受到一次警告,求从\(1\)到\(n\)最少受到多少次警告. 输入格式 第一行,两个整…

题目大意: 给定n个点m条边的有向图 有两个GPS 分别认为 A[i]到B[i] 的一条边的花费是P[i].Q[i] 当当前走的边不是GPS认为的最短路上的边就会被警告 即两个GPS都不认为是最短路上的边时 会被警告两次 求从点1走到点n被警告次数最少是多少次 https://blog.csdn.net/oakley_/article/details/52510465 按P[i]反向建图 再从n跑最短路到1 然后遍历所有的边判断将不是最短路的边C[i]+1 Q[i]也同样 最后按C[i]从1跑最…

传送门 图论模拟题. 这题直接写3个(可以压成一个)spfa" role="presentation" style="position: relative;">spfaspfa,前两个把题上的p,q" role="presentation" style="position: relative;">p,qp,q分别当做边权来跑,然后最后一次将前两次标记过两次的边边权设为0,标记过一次的边权设为1,…