蓝桥杯 城市建设

  1 #include<bits/stdc++.h>
  2 using namespace std;
  3 const int maxn = 1e5 + 10;
  4 const int INF = 1e9;
  5 struct Edge
  6 {
  7     int u, v;
  8     int dis;
  9 }edge[maxn * 100];
 10 int n, m;
 11 int cnt;
 12 int port[maxn];
 13 vector<int> vec;
 14 int fa[maxn];
 15 int ans;
 16 
 17 bool cmp(Edge a, Edge b)
 18 {
 19     return a.dis < b.dis;
 20 }
 21 
 22 
 23 void init()
 24 {
 25     for(int i = 0; i <= n; i++)
 26         fa[i] = i;
 27 }
 28 
 29 
 30 int findfa(int x)
 31 {
 32     if(fa[x] == x)
 33         return x;
 34     else
 35         return fa[x] = findfa(fa[x]);
 36 }
 37 
 38 int Kruskal(int edgenum, int vernum)
 39 {
 40     int num = 0;
 41     int res = 0;
 42     for(int i = 0; i < edgenum; i++)
 43     {
 44         //if(num == n - 1)    break;
 45         int x = edge[i].u;
 46         int y = edge[i].v;
 47         int d = edge[i].dis;
 48 
 49         int fx = findfa(x);
 50         int fy = findfa(y);
 51 
 52         if(fx != fy)
 53         {
 54             fa[fy] = fx;
 55             res += d;
 56             //ans += d;
 57             num++;
 58 
 59         }
 60         else if(d < 0)
 61             res += d;
 62             //ans += d;
 63     }
 64     if(num == vernum - 1)    return res;
 65     else    return -1;
 66     //return num;
 67 }
 68 
 69 
 70 int main()
 71 {
 72     int a, b, c;
 73 
 74     cin >> n >> m;
 75     for(int i = 0; i < m; i++)
 76     {
 77         scanf("%d%d%d", &a, &b, &c);
 78         edge[i].u = a;
 79         edge[i].v = b;
 80         edge[i].dis = c;
 81     }
 82     cnt = m;
 83 
 84     for(int i = 1; i <= n; i++)
 85     {
 86         scanf("%d", &port[i]);
 87         if(port[i] < 0) continue;
 88         edge[cnt].u = 0;
 89         edge[cnt].v = i;
 90         edge[cnt].dis = port[i];
 91         cnt++;
 92     }
 93     sort(edge, edge + m, cmp);
 94     init();
 95     ans = Kruskal(m, n);
 96     //int flag = Kruskal(m, n);
 97     sort(edge, edge + cnt, cmp);
 98     init();
 99     //int t = flag;
100     int mid = ans;
101     ans = Kruskal(cnt, n + 1);
102     //flag = Kruskal(cnt, n + 1);
103     if(mid == -1)
104     {
105         cout << ans << endl;
106     }
107     else
108     {
109         ans = min(ans, mid);
110         cout << ans << endl;
111     }
112 
113     return 0;
114 }