使用dfs计算连通分量的数量
1 #pragma warning(disable:4996) 2 #define _CRT_SECURE_NO_WARNINGS 3 4 #include <iostream> 5 #include <algorithm> 6 #include <cmath> 7 #include <vector> 8 #include <map> 9 #include <set> 10 #include <unordered_set> 11 #include <unordered_map> 12 #include <queue> 13 #include <cmath> 14 #include <string> 15 #define INFINITE 65535 16 #define mod 1000000007 17 using namespace std; 18 vector<int> edge[10010], maxd; 19 int depth = 0; 20 int vis[10010] = { 0 }; 21 void dfs(int s, int dep) 22 { 23 vis[s] = 1; 24 if (dep > depth)depth = dep; 25 for (int i = 0; i < edge[s].size(); ++i){ 26 if (!vis[edge[s][i]]){ 27 dfs(edge[s][i], dep + 1); 28 } 29 } 30 } 31 int main() 32 { 33 int n; 34 cin >> n; 35 maxd.resize(n+1); 36 for (int i = 0; i < n - 1; ++i){ 37 int a, b; 38 cin >> a >> b; 39 edge[a].push_back(b); 40 edge[b].push_back(a); 41 } 42 int max = 0; 43 int num = 0; 44 for (int i = 1; i <= n; ++i){ 45 fill(vis, vis + 10010, 0); 46 depth = 0; 47 dfs(i, 0); 48 maxd[i] = depth; 49 if (depth > max)max = depth; 50 } 51 fill(vis, vis + 10010, 0); 52 for (int i = 1; i <= n; ++i){ 53 if (!vis[i]) { 54 ++num; 55 dfs(i, 0); 56 } 57 } 58 vector<int> res; 59 if (num == 1) { 60 for (int i = 1; i <= n; ++i) 61 if (maxd[i] == max) 62 res.push_back(i); 63 for (int it : res) 64 cout << it << endl; 65 } 66 else{ 67 cout << "Error: "<< num <<" components"<< endl; 68 } 69 return 0; 70 }
使用并查集计算连通分量的数量
1 #pragma warning(disable:4996) 2 #define _CRT_SECURE_NO_WARNINGS 3 4 #include <iostream> 5 #include <algorithm> 6 #include <cmath> 7 #include <vector> 8 #include <map> 9 #include <set> 10 #include <unordered_set> 11 #include <unordered_map> 12 #include <queue> 13 #include <cmath> 14 #include <string> 15 #define INFINITE 65535 16 #define mod 1000000007 17 using namespace std; 18 vector<int> edge[10010], maxd, father; 19 int depth = 0; 20 int vis[10010] = { 0 }; 21 int findRoot(int i) 22 { 23 if (father[i] == i) { 24 return i; 25 } 26 int temp = findRoot(father[i]); 27 father[i] = temp;//压缩路径 28 return temp; 29 } 30 void unionSet(int a, int b) 31 { 32 int ra = findRoot(a); 33 int rb = findRoot(b); 34 if (ra != rb) { 35 father[ra] = rb; 36 } 37 } 38 void dfs(int s, int dep) 39 { 40 vis[s] = 1; 41 if (dep > depth)depth = dep; 42 for (int i = 0; i < edge[s].size(); ++i) { 43 if (!vis[edge[s][i]]) { 44 45 unionSet(s, edge[s][i]); 46 dfs(edge[s][i], dep + 1); 47 } 48 } 49 } 50 int main() 51 { 52 int n; 53 cin >> n; 54 maxd.resize(n + 1); father.resize(n + 1); 55 for (int i = 1; i <= n; ++i) father[i] = i; 56 for (int i = 0; i < n - 1; ++i){ 57 int a, b; 58 cin >> a >> b; 59 edge[a].push_back(b); 60 edge[b].push_back(a); 61 } 62 int max = 0; 63 int num = 0; 64 for (int i = 1; i <= n; ++i){ 65 fill(vis, vis + 10010, 0); 66 depth = 0; 67 dfs(i, 0); 68 maxd[i] = depth; 69 if (depth > max)max = depth; 70 } 71 for (int i = 1; i <= n; ++i) { 72 if (father[i] == i)++num; 73 } 74 if (num == 1) {//全部结点连通 75 vector<int> res; 76 for (int i = 1; i <= n; ++i) 77 if (maxd[i] == max) 78 res.push_back(i); 79 for (int it : res) 80 cout << it << endl; 81 } 82 else{ 83 cout << "Error: "<< num <<" components"<< endl; 84 } 85 return 0; 86 }