AcWing 858. Prim算法求最小生成树
原题链接
简单
作者:
no_one
,
2022-08-07 17:40:06
,
所有人可见
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阅读 114
最小生成树
#include<iostream>
#include<algorithm>
#include<cstring>
using namespace std;
const int N = 510, ins = 0x3f3f3f3f;
int g[N][N];
int d[N];
bool yin[N];
int n, m;
int prim()
{
int res = 0;
for(int i = 0; i < n; i ++)
{
int t = -1;
for(int j = 1; j <= n; j ++)
if( !yin[j] && (t == -1 || d[t] > d[j] ) )
t = j;
if(i && d[t] == ins) return ins;
if(i) res += d[t];
yin[t] = true;
for(int j = 1; j <= n; j ++) d[j] = min(d[j], g[t][j]);
}
return res;
}
int main()
{
cin >> n >> m;
memset(d, 0x3f, sizeof d);
memset(g, 0x3f, sizeof g);
while(m --)
{
int a, b, c;
scanf("%d%d%d",&a,&b,&c);
g[a][b] = g[b][a] = min(g[a][b], c);
}
int t = prim();
if(t == 0x3f3f3f3f) puts("impossible");
else cout << t << endl;
return 0;
}