AcWing 859. Kruskal算法求最小生成树
原题链接
简单
作者:
芝居気
,
2021-12-05 19:28:51
,
所有人可见
,
阅读 124
#include<iostream>
#include<algorithm>
using namespace std;
#define db(x) cout<<#x<<" = "<<x<<" | ";
const int N = 200005;
int p[N];
int n, m;
int ans;
struct edge
{
int a, b, c;
bool operator < (const edge &a)const
{
return c < a.c;
}
}e[N];
int find(int x)
{
if(x!=p[x]) p[x]=find(p[x]);
return p[x];
}
int Kruskal()
{
int cnt=0;
for (int i = 0; i < m; i++)//是遍历所有的边,所以结束条件需要是m
{
int a = e[i].a, b = e[i].b, c = e[i].c;
// db(a) db(b) cout<<endl;db(p[a]) db(p[b])
// db(find(a)) db(find(b))cout<<endl;
if (find(a) != find(b))
{
cnt++;
ans += c;
p[find(a)] = find(b);
}
}
// db(cnt);
// db(ans);
if (cnt >= n - 1) return ans;
else return 0x3f3f3f3f;
}
int main()
{
cin >> n >> m;
for (int i = 1; i <= n; i++)
{
p[i] = i;
}
for (int i = 0; i < m; i++)
{
int a, b, c;
cin >> a >> b >> c;
e[i] = { a,b,c };
}
sort(e, e + m);
if (Kruskal() == 0x3f3f3f3f)cout << "impossible";
else cout << ans;
}