PAT A 1013. Battle Over Cities (25)【并查集】
https://www.patest.cn/contests/pat-a-practise/1013
思路：并查集合并
1 #include<set> 2 #include<map> 3 #include<queue> 4 #include<algorithm> 5 #include<string> 6 #include<string.h> 7 using namespace std; 8 9 int n;//number of city 10 int m;//number of edge 11 int k;//number of query 12 13 typedef struct Edge 14 { 15 int v; 16 Edge(int _v) :v(_v){}; 17 }Edge; 18 typedef struct Node 19 { 20 int parent; 21 }Node; 22 vector<Node> city; 23 void InitSet() 24 { 25 city.resize(n); 26 for (int i = 0; i < n; i++) 27 city[i].parent = i;//独立离散连通域 28 } 29 30 int FindSet(int x) 31 { 32 if (city[x].parent != x) 33 { 34 int top = FindSet(city[x].parent); 35 city[x].parent = top; 36 } 37 return city[x].parent; 38 } 39 void UnionSet(int x, int y) 40 { 41 int a = FindSet(x); 42 int b = FindSet(y); 43 if (a != b)city[a].parent = b; 44 } 45 int main() 46 { 47 scanf("%d%d%d", &n, &m, &k); 48 vector<vector<Edge>> edge; 49 edge.resize(n); 50 for (int i = 0; i < m;i++) 51 { 52 int a, b; 53 scanf("%d%d", &a, &b); 54 a--, b--; 55 edge[a].push_back(Edge(b)); 56 edge[b].push_back(Edge(a)); 57 } 58 for (int i = 0; i < k; i++) 59 { 60 int q; 61 scanf("%d", &q); 62 q--; 63 InitSet(); 64 for (int u = 0; u < n; u++) 65 { 66 for (int j = 0; j < edge[u].size(); j++) 67 { 68 int v = edge[u][j].v; 69 if (u != q&&v != q)UnionSet(u, v); 70 } 71 } 72 set<int> parentSet; 73 for (int j = 0; j < n; ++j) 74 //must be care for this, for consistency we must get the root via FindSet function instead of city[j].parent 75 parentSet.insert(FindSet(j)); 76 printf("%d\n", parentSet.size() - 2); 77 } 78 return 0; 79 } 80 81 82 83 84
