BZOJ 1086 王室联邦(块状树)

题意:

$给定一颗N\le 1000个点的树$
$要求将这棵树分成一些块,使每块大小在[B, 3B]之间,1\le B\le N$

分析:

$PO娘的博客讲的很清楚辣,手把手教你块状树$
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//
// Created by TaoSama on 2016-08-08
// Copyright (c) 2016 TaoSama. All rights reserved.
//
#pragma comment(linker, "/STACK:102400000,102400000")
#include <algorithm>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <string>
#include <set>
#include <vector>
using namespace std;
#define pr(x) cout << #x << " = " << x << " "
#define prln(x) cout << #x << " = " << x << endl
const int N = 1e3 + 10, INF = 0x3f3f3f3f, MOD = 1e9 + 7;
int n, B;
vector<int> G[N];
int stk[N], top;
int blocks, id[N], rt[N];
void dfs(int u, int f) {
int btm = top;
for(int i = 0; i < G[u].size(); ++i) {
int v = G[u][i];
if(v == f) continue;
dfs(v, u);
if(top - btm >= B) {
rt[++blocks] = u;
while(top != btm) {
int v = stk[top--];
id[v] = blocks;
}
}
}
stk[++top] = u;
}
int main() {
#ifdef LOCAL
freopen("C:\\Users\\TaoSama\\Desktop\\in.txt", "r", stdin);
// freopen("C:\\Users\\TaoSama\\Desktop\\out.txt","w",stdout);
#endif
ios_base::sync_with_stdio(0);
scanf("%d%d", &n, &B);
for(int i = 1; i < n; ++i) {
int u, v; scanf("%d%d", &u, &v);
G[u].push_back(v);
G[v].push_back(u);
}
dfs(1, 0);
while(top) id[stk[top--]] = blocks;
printf("%d\n", blocks);
for(int i = 1; i <= n; ++i) printf("%d%c", id[i], " \n"[i == n]);
for(int i = 1; i <= blocks; ++i) printf("%d%c", rt[i], " \n"[i == blocks]);
return 0;
}

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