Submission #91893

#	Time	Username	Problem	Language	Result	Execution time	Memory
91893		emil_physmath	Birthday gift (IZhO18_treearray)	C++17	56 / 100	85 ms	888 KiB

treearray

#include <iostream>
#include <stdio.h>
#include <vector>
using namespace std;
const int MAXN=2005;

int n, l, timer, a[MAXN], tin[MAXN], tout[MAXN];
vector<int> nei[MAXN], up[MAXN];

int lca(int u, int v);
void dfs (int u, int p=1);
bool upper (int u, int v);
int main()
{
	int m, q;
	cin>>n>>m>>q;
	for (int i=1; i<n; i++)
	{
		int u, v;
		scanf("%d%d", &u, &v);
		nei[u].push_back(v);
		nei[v].push_back(u);
	}
	l=1;
	while((1<<l)<=n)
		l++;
	for(int i=1; i<=n; i++)
		up[i].resize(l+1);
	dfs(1);
	for (int i=1; i<=m; i++)
		scanf("%d", a+i);
	int type, pos, L, R, v, ans;
	while (q--)
	{
		scanf("%d", &type);
		if (type==1)
		{
			scanf("%d%d", &pos, &v);
			a[pos]=v;
		}
		else
		{
			scanf("%d%d%d", &L, &R, &v);
			ans=-1;
			for (int i=L; i<R; i++)
				if (lca(a[i], a[i+1])==v)
				{
					ans=i;
					break;
				}
			if (ans==-1)
			{
				for (int i=L; i<=R; i++)
					if (a[i]==v)
					{
						ans=i;
						break;
					}
				if (ans==-1)
					printf("-1 -1\n");
				else
					printf("%d %d\n", ans, ans);
			}
			else
				printf("%d %d\n", ans, ans+1);
		}
	}

	char I;
	cin >> I;
	return 0;
}

void dfs(int u, int p) {
	tin[u]=++timer;
	up[u][0]=p;
	for (int i=1; i<=l; i++)
		up[u][i]=up[up[u][i-1]][i-1];
	for (int i=0; i<nei[u].size(); i++)
		if (nei[u][i]!=p)
			dfs(nei[u][i], u);
	tout[u]=++timer;
}

bool upper(int u, int v) {
	return tin[u]<=tin[v] && tout[u]>=tout[v];
}

int lca(int u, int v) {
	if (upper(u, v))  return u;
	if (upper(v, u))  return v;
	for (int i=l; i>=0; i--)
		if (!upper (up[u][i], v))
			u=up[u][i];
	return up[u][0];
}

Compilation message (stderr)

treearray.cpp: In function 'void dfs(int, int)':
treearray.cpp:79:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i=0; i<nei[u].size(); i++)
                ~^~~~~~~~~~~~~~
treearray.cpp: In function 'int main()':
treearray.cpp:20:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d", &u, &v);
   ~~~~~^~~~~~~~~~~~~~~~
treearray.cpp:31:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d", a+i);
   ~~~~~^~~~~~~~~~~
treearray.cpp:35:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d", &type);
   ~~~~~^~~~~~~~~~~~~
treearray.cpp:38:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d%d", &pos, &v);
    ~~~~~^~~~~~~~~~~~~~~~~~
treearray.cpp:43:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d%d%d", &L, &R, &v);
    ~~~~~^~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 12 / 12
• Subtask 2: 18 / 18
• Subtask 3: 26 / 26
• Subtask 4: 0 / 44