计蒜客42552

include

include

include

include

include

include

include

include

include

include

include

include

//#include

include

include

pragma GCC optimize(2)

define up(i,a,b) for(int i=a;i<b;i++)

define dw(i,a,b) for(int i=a;i>b;i--)

define upd(i,a,b) for(int i=a;i<=b;i++)

define dwd(i,a,b) for(int i=a;i>=b;i--)

//#define local
typedef long long ll;
typedef unsigned long long ull;
const double esp = 1e-6;
const double pi = acos(-1.0);
const int INF = 0x3f3f3f3f;
const int inf = 1e9;
using namespace std;
ll read()
{
char ch = getchar(); ll x = 0, f = 1;
while (ch<'0' || ch>'9') { if (ch == '-')f = -1; ch = getchar(); }
while (ch >= '0' && ch <= '9') { x = x * 10 + ch - '0'; ch = getchar(); }
return x * f;
}
typedef pair<int, int> pir;

define lson l,mid,root<<1

define rson mid+1,r,root<<1|1

define lrt root<<1

define rrt root<<1|1

const int N = 2e5 + 10;
int n;
struct edge {
int v, next;
}edge[N << 1];
int head[N], cnt;
int sz[N], son[N], par[N], ans[N], anss[N];
int SIZE, rt;
int dp[N];
void addedge(int u, int v) {
edge[cnt].v = v;
edge[cnt].next = head[u];
head[u] = cnt++;
}
void cal(int u, int x) {
if (x == 0) {
ans[u] = u; return;
}
int mx = INF;
int rt = x;
while (x != par[u]&&max(sz[son[x]],sz[u]-sz[x])<=mx) {
if (max(sz[son[x]], sz[u] - sz[x]) == mx) {
anss[u] = x;
}
else {
mx = max(sz[son[x]], sz[u] - sz[x]);
ans[u] = x;
}
x = par[x];
}
}
void dfs1(int u, int fa) {
sz[u] = 1;
par[u] = fa;
for (int i = head[u]; ~i; i = edge[i].next) {
int v = edge[i].v;
if (v == fa)continue;
dfs1(v, u);
sz[u] += sz[v];
if (son[u] == -1 || sz[son[u]] < sz[v])son[u] = v;
}
}
void dfs2(int u, int fa) {
for (int i = head[u]; ~i; i = edge[i].next) {
int v = edge[i].v;
if (v == fa)continue;
dfs2(v, u);
}
if (son[u] != -1) {
cal(u, ans[son[u]]);
}
else cal(u, 0);
}
int main() {
n = read();
memset(head, -1, sizeof(head));
memset(son, -1, sizeof(son));
int u, v;
SIZE = n;
upd(i, 1, n-1) {
u = read(), v = read();
addedge(u, v); addedge(v, u);
}
dfs1(1, 0);
dfs2(1, 0);
upd(i, 1, n) {
if (anss[i] && anss[i] < ans[i])swap(anss[i], ans[i]);
printf("%d", ans[i]);
if (anss[i])
printf(" %d\n", anss[i]);
else puts("");
}
return 0;
}