Balancing Act 树的重心
#include <iostream> #include <vector> #include <algorithm> #include <string> #include <set> #include <queue> #include <map> #include <sstream> #include <cstdio> #include <cstring> #include <numeric> #include <cmath> #include <iomanip> #include <deque> #include <bitset> #include <cassert> //#include <unordered_set> //#include <unordered_map> #define ll long long #define pii pair<int, int> #define rep(i,a,b) for(int i=a;i<=b;i++) #define dec(i,a,b) for(int i=a;i>=b;i--) #define forn(i, n) for(int i = 0; i < int(n); i++) using namespace std; int dir[4][2] = { { 1,0 },{ 0,1 } ,{ 0,-1 },{ -1,0 } }; const long long INF = 0x7f7f7f7f7f7f7f7f; const int inf = 0x3f3f3f3f; const double pi = acos(-1.0); const double eps = 1e-6; const int mod = 1e9 + 7; inline ll read() { ll x = 0; bool f = true; char c = getchar(); while (c < '0' || c > '9') { if (c == '-') f = false; c = getchar(); } while (c >= '0' && c <= '9') x = (x << 1) + (x << 3) + (c ^ 48), c = getchar(); return f ? x : -x; } inline ll gcd(ll m, ll n) { return n == 0 ? m : gcd(n, m % n); } void exgcd(ll A, ll B, ll& x, ll& y) { if (B) exgcd(B, A % B, y, x), y -= A / B * x; else x = 1, y = 0; } inline int qpow(int x, ll n) { int r = 1; while (n > 0) { if (n & 1) r = 1ll * r * x % mod; n >>= 1; x = 1ll * x * x % mod; } return r; } inline int inv(int x) { return qpow(x, mod - 2); } ll lcm(ll a, ll b) { return a * b / gcd(a, b); } /**********************************************************/ const int N = 2e4 + 5; int sz[N],wt[N]; int n, rt; void getcentroid(int x, int fa,vector<vector<int> >& g) { sz[x] = 1; wt[x] = 0; for (int i = 0; i < g[x].size(); i++) { int to = g[x][i]; if (to != fa) { getcentroid(to, x, g); sz[x] += sz[to]; wt[x] = max(wt[x], sz[to]); } } wt[x] = max(wt[x], n - sz[x]); if (rt == 0 || wt[x] < wt[rt])//rt是重心编号 rt = x; } int main() { //ios::sync_with_stdio(false);cin.tie(0); cout.tie(0); int T; cin >> T; while (T--) { memset(wt, 0, sizeof(wt)); memset(sz, 0, sizeof(sz)); cin >> n; rt = 0; vector<vector<int> > g(n + 1); rep(i, 1, n - 1) { int u, v; scanf("%d%d", &u ,& v); g[u].push_back(v); g[v].push_back(u); } getcentroid(1, -1, g); printf("%d %d\n", rt, wt[rt]); } }