C题思路：生成树上的dfs，完全没见过，留作复习
代码：
#include<stdio.h>
#include<iostream>
#include<string.h>
#include<algorithm>
#include<queue>
#include<string>
#include<vector>
#define maxn 210000
using namespace std;
int n;
vector<int>aaa[maxn];
int power[maxn];
int color[maxn];
void dfs(int x, int fa) { //对第x个节点的子节点们开始染色，x的父节点是fA
int c = 1;
for (int i = 0; i < aaa[x].size(); i++) {
int temp = aaa[x][i];
if (color[temp] != 0)continue;
while (c == color[x] || c == color[fa])c++;
color[temp] = c;
dfs(temp, x);
c++;
}
}
int ans;
int main() {
memset(color, 0, sizeof(color));
memset(power, 0, sizeof(power));
ans = 0;
scanf("%d", &n);
int a, b;
for (int i = 1; i < n; i++) {
scanf("%d %d", &a, &b);
power[a]++; power[b]++;
ans = max(ans, max(power[a], power[b]));
aaa[a].push_back(b);
aaa[b].push_back(a);
}
ans++;
cout << ans << endl;
dfs(1, 0);
for (int i = 1; i <= n; i++) {
if (i != 1)printf(" ");
printf("%d", color[i]);
}
printf("
");
}