Time Limit: 2 Seconds
Memory Limit: 65536 KB
A city is served by a number of fire stations. Some residents have complained
that the distance from their houses to the nearest station is too far, so a new
station is to be built. You are to choose the location of the fire station so
as to reduce the distance to the nearest station from the houses of the disgruntled
The city has up to 500 intersections, connected by road segments of various lengths.
No more than 20 road segments intersect at a given intersection. The location
of houses and firestations alike are considered to be at intersections (the travel
distance from the intersection to the actual building can be discounted). Furthermore,
we assume that there is at least one house associated with every intersection.
There may be more than one firestation per intersection.
The first line of input contains two positive integers: f,the number of existing
fire stations (f <= 100) and i, the number of intersections (i <= 500).
The intersections are numbered from 1 to i consecutively. f lines follow; each
contains the intersection number at which an existing fire station is found.
A number of lines follow, each containing three positive integers: the number
of an intersection, the number of a different intersection, and the length of
the road segment connecting the intersections. All road segments are two-way
(at least as far as fire engines are concerned), and there will exist a route
between any pair of intersections.
Subsequent test cases are separated with a single blank line.
You are to output a single integer for each test case: the lowest intersection
number at which a new fire station should be built so as to minimize the maximum
distance from any intersection to the nearest fire station.
1 2 10
2 3 10
3 4 10
4 5 10
5 6 10
6 1 10
Source: University of Waterloo Local Contest 1999.09.25