High-speed rail network
description:
Nation-building high-speed rail network, which consists of a number of high-speed rail line connecting the city. Existing high-speed rail construction could be classified as a statistical table, the table lists each of the two cities a high-speed rail line directly connected. Construction is to target countries can achieve high-speed rail traffic between the two cities per country (but not necessarily directly connected to high-speed rail line, as long as indirectly through high-speed rail line up to). Ask the minimum number of high-speed rail line would also like to build?
Enter a description:
Test line 1 are given two positive integers, respectively, the number of cities is N (<1000) and the number of existing high-speed rail line M. M then M rows corresponding to high-speed rail lines, each line is given a pair of positive integers, respectively the two cities article directly connected high-speed line number. For simplicity, the city numbered from 1 to N.
Output Description:
On the line of output also the least number of high-speed rail lines need to build.
Sample input:
9 8
1 2
1 3
2 4
3 4
5 7
5 6
6 7
8 9
Sample output:
2
To achieve prompt:
The number of the real problem for the sake of reducing a communication component, available depth-first or breadth-first search to solve, can also be solved MFSet.
#include<stdio.h>
#include<stdlib.h>
int vset[100];
int findset(int x)
{
while (vset[x] != 0)
x = vset[x];
return x;
}
int main ()
{
int m, n, i, a, b, va, vb, count;
scanf("%d", &n);
for (i = 0; i < n; i++)
vset[i] = 0;
scanf("%d", &m);
for (i = 0; i < m; i++)
{
scanf("%d %d", &a, &b);
va = findset(a);
vb = findset(b);
if (va != vb)
vset[va] = vb;
}
count = 0;
for (i = 0; i < n; i++)
{
if (vset[i] == 0)
count++;
}
printf("%d", count-1);
return 0;
}