题目大意：
判断n个点能否被n-1条边相连，且每条边都平行于坐标轴。
分析：
因为最多也就30个点，所以把边延伸地很长即可：
#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define PII pair<int, int>
const int maxn = 50;
vector<int> v[maxn];
int nx[] = {0, 1, 0, -1};
int ny[] = {1, 0, -1, 0};
bool vis[maxn];
PII ans[maxn];
void dfs(int u, int lev, int x, int y, int pre)
{vis[u] = true;ans[u] = (PII){x, y};int dir = 0, to;for(int i = 0; i < v[u].size(); i++){to = v[u][i];if(vis[to])continue;if(dir == pre)dir++;dfs(to, lev-1, x + (1<<lev)*nx[dir], y + (1<<lev)*ny[dir], (dir+2) %4);dir++;}
}
int main()
{int n, x, y;cin >> n;for(int i = 0; i < n-1; i++){scanf("%d%d", &x, &y);v[x].pb(y);v[y].pb(x);}for(int i = 0; i < n; i++)if(v[i].size() > 4)return 0*printf("NO\n");printf("YES\n");dfs(1, 30, 0, 0, -1);for(int i = 1; i <= n; i++)cout << ans[i].first << " " << ans[i].second << endl;return 0;
}