[USACO 102]Agri-Net
OJ题号：POJ1258、洛谷1546
思路：Kruskal。
1 #include<cstdio> 2 #include<utility> 3 #include<vector> 4 #include<algorithm> 5 #define w first 6 #define a second.first 7 #define b second.second 8 typedef std::pair<int,std::pair<int,int> > Edge; 9 const int N=100; 10 int n; 11 std::vector<Edge> e; 12 class UnionFindSet { 13 private: 14 int anc[N]; 15 public: 16 UnionFindSet(int n) { 17 for(int i=0;i<n;i++) anc[i]=i; 18 } 19 int Find(int x) { 20 return (x==anc[x])?x:(anc[x]=Find(anc[x])); 21 } 22 void Union(int x,int y) { 23 anc[Find(y)]=Find(x); 24 } 25 }; 26 int main() { 27 scanf("%d",&n); 28 for(int i=0;i<n;i++) { 29 for(int j=0;j<n;j++) { 30 int c; 31 scanf("%d",&c); 32 if(i<j) { 33 e.push_back(std::make_pair(c,std::make_pair(i,j))); 34 } 35 } 36 } 37 UnionFindSet s(n); 38 std::sort(e.begin(),e.end()); 39 int ans=0; 40 for(int i=0;i<(int)e.size();i++) { 41 if(s.Find(e[i].a)==s.Find(e[i].b)) continue; 42 ans+=e[i].w; 43 s.Union(e[i].a,e[i].b); 44 } 45 printf("%d\n",ans); 46 return 0; 47 }
