原题链接:畅通工程
题目分析:典型的并查集模版题,这里就不详细叙述了。对算法本身不太了解的可以参考这篇文章:并查集算法详解
代码如下:
#include <iostream>
#include <algorithm>
#include <cstring>
using namespace std;
const int MAX = 1000;
int father[MAX];
int getfather(int v) {
if (father[v] == v)
return v;
else
{
father[v] = getfather(father[v]); //路径压缩
return father[v];
}
}
void Union(int x,int y) {
int fx = getfather(x);
int fy = getfather(y);
if(fy != fx)
father[fx] = fy;
}
void init(int n) {
for (int i = 0; i < n; i++)
father[i] = i;
}
int main() {
int n, m, a, b;
while (cin >> n >> m && n) {
memset(father, 0, sizeof(father));
init(n);
for(int i = 0; i < m; i++) {
cin >> a >> b;
Union(a, b);
}
int ans = 0;
for(int i = 0; i < n; i++)
if(father[i] == i)
ans++;
cout << ans - 1 << endl;
}
return 0;
}