Submission #106094

#	Time	Username	Problem	Language	Result	Execution time	Memory
106094		mzhao	Mergers (JOI19_mergers)	C++11	0 / 100	27 ms	24028 KiB

mergers

#include <bits/stdc++.h>
using namespace std;

#ifdef DEBUG
#define D(x...) printf(x)
#else
#define D(x...)
#endif

#define MN 500100
#define x first
#define y second

int N, K, S[MN];
vector<int> adj[MN];

int tot[MN], cnt[MN], ans, dep[MN], par[MN];
bool bad[MN];

void dfs(int n, int p, int d) {
	dep[n] = d;
	par[n] = p;
	int cur[8];
	for (int i = 1; i <= K; i++) cur[i] = cnt[i];
	cnt[S[n]]++;
	for (int i : adj[n]) if (i != p) {
		dfs(i, n, d+1);
	}
	for (int i = 1; i <= K; i++) cur[i] = cnt[i]-cur[i];
	if (n == 1) return;
	bool f = 1;
	for (int i = 1; i <= K; i++) if (cur[i] && cur[i] != tot[i]) {
		f = 0;
		break;
	}
	bad[n] = f;
}

pair<int, int> dp[MN];
pair<int, int> bpos;
int bval;

void dfs2(int n, int p) {
	pair<int, int> b1 = {0, 0}, b2 = {0, 0};
	for (int i : adj[n]) if (i != p) {
		dfs2(i, n);
		if (dp[i].x >= b1.x) {
			b2 = b1;
			b1 = dp[i];
		} else if (dp[i].x >= b2.x) {
			b2 = dp[i];
		}
	}
	if (b2.y && b1.x+b2.x > bval) {
		bval = b1.x+b2.x;
		bpos = {b1.y, b2.y};
	}
	if (b1.x == 0 && bad[n]) {
		b1 = {1, n};
	} else if (bad[n]) {
		b1.x++;
	}
	dp[n] = b1;
}

void rem() {
	int a = bpos.x, b = bpos.y;
	if (dep[a] < dep[b]) swap(a, b);
	while (dep[a] > dep[b]) {
		bad[a] = 0;
		a = par[a];
	}
	while (a != b) {
		bad[a] = bad[b] = 0;
		a = par[a]; b = par[b];
	}
}

int main() {
	scanf("%d%d", &N, &K);
	assert(N <= 100);
	for (int i = 1, A, B; i < N; i++) {
		scanf("%d%d", &A, &B);
		adj[A].push_back(B);
		adj[B].push_back(A);
	}
	for (int i = 1; i <= N; i++) {
		scanf("%d", &S[i]);
		tot[S[i]]++;
	}
	dfs(1, 0, 0);
	while (1) {
		for (int j = 1; j <= N; j++) dp[j] = {0, 0};
		bval = 0;
		bpos = {0, 0};
		dfs2(1, 0);
		D("%d %d %d\n", bval, bpos.x, bpos.y);
		if (!bval) {
			if (dp[1].x) ans++;
			break;
		} else {
			rem();
			ans++;
		}
	}
	printf("%d\n", (ans+1)/2);
}

Compilation message (stderr)

mergers.cpp: In function 'int main()':
mergers.cpp:80:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d", &N, &K);
  ~~~~~^~~~~~~~~~~~~~~~
mergers.cpp:83:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d", &A, &B);
   ~~~~~^~~~~~~~~~~~~~~~
mergers.cpp:88:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d", &S[i]);
   ~~~~~^~~~~~~~~~~~~

• Subtask 1: 0 / 10
• Subtask 2: 0 / 24
• Subtask 3: 0 / 14
• Subtask 4: 0 / 22
• Subtask 5: 0 / 30