MICEMAZE  Mice and Maze
A set of laboratory mice is being trained to escape a maze. The maze is made up of cells, and each cell is connected to some other cells. However, there are obstacles in the passage between cells and therefore there is a time penalty to overcome the passage Also, some passages allow mice to go oneway, but not the other way round.
Suppose that all mice are now trained and, when placed in an arbitrary cell in the maze, take a path that leads them to the exit cell in minimum time.
We are going to conduct the following experiment: a mouse is placed in each cell of the maze and a countdown timer is started. When the timer stops we count the number of mice out of the maze.
Problem
Write a program that, given a description of the maze and the time limit, predicts the number of mice that will exit the maze. Assume that there are no bottlenecks is the maze, i.e. that all cells have room for an arbitrary number of mice.
Input
The maze cells are numbered $1, 2, \ldots, N$, where $N$ is the total number of cells. You can assume that $N \le 100$.
The first three input lines contain $N$, the number of cells in the maze, $E$, the number of the exit cell, and the starting value $T$ for the countdown timer (in some arbitrary time unit).
The fourth line contains the number $M$ of connections in the maze, and is followed by $M$ lines, each specifying a connection with three integer numbers: two cell numbers $a$ and $b$ (in the range $1, \ldots, N$) and the number of time units it takes to travel from $a$ to $b$.
Notice that each connection is oneway, i.e., the mice can't travel from $b$ to $a$ unless there is another line specifying that passage. Notice also that the time required to travel in each direction might be different.
Output
The output consists of a single line with the number of mice that reached the exit cell $E$ in at most $T$ time units.
Example
Input: 4 2 1 8 1 2 1 1 3 1 2 1 1 2 4 1 3 1 1 3 4 1 4 2 1 4 3 1 Output: 3
hide comments
sapjv:
20191125 07:26:19
Can someone explain why we are reversing the edges before implementing dijkstra ? I am not getting it. Please explain it with one simple example. Thanks for the help in advance ! 

harry_shit:
20191123 09:33:42
dijkstra with reverse edges :) 

purplecs:
20191113 16:43:19
Apply FloydWarshall and then


scorpy1:
20190816 18:35:53
Hint: reverse the edges is important! 

masterchef2209:
20190513 06:01:21
AC in 1 go :D


mr_pandey:
20190122 15:05:13
@vaishcr7 the shortest path from 2 to 1 is having length 3 in your test case. Thus the answer must be 2.


phoemur:
20181202 21:20:23
SPOJ toolkit is a mess for this problem... Many wrong and even invalid testcases...


vaishcr7:
20181019 19:32:42
After many tries , I am still getting WA. I have used simple bfs on exit cell, reversing the edges and tried out all from spojtoolkit. I am using java b/w. I dont know what to expect for the below test case but spojtoolkit says 2. Question doesn't answer about overwriting edges between two vertices. Also I'm not sure which test case is giving me errors. This is the test case though:


sachinspoj:
20181007 05:11:57
solved with bfs :)


gopikrishna_p:
20180716 07:35:55
poor english 
Added by:  overwise 
Date:  20071004 
Time limit:  0.310s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: ERL JSRHINO NODEJS PERL6 VB.NET 
Resource:  ACM ICPC  SWERC 2001 