481 - What Goes Up

[Ivo Sluganovic]

How do I solve the 481 (What goes up) problem more efficently?
I implemented the standard LIS algorithm, but it seems to be too slow.
I've tried implementing it using linked lists and some other things to improve the time, but stil keep on getting TLE.

Can anybody give me an idea to fasten my program up?

How did someone get 0.00.086 on this?

[Andrew Neitsch]

There's an O(n log n) algorithm for this.

Super-fast times are usually I/O optimization or tables or something like that. Don't worry about it.

[Morning]

i used the DP(LIS) which is O(n^2),that algorithm may cause TLE,but why i got WA?

is my algorithm okay?

Code: Select all

#include <iostream>
using namespace std;

int height[10000];
int len[10000];
int pre[10000];
int limit;
int i,j;
int maxlen;
int tail;

void output(int i)
{
	if(pre[i] == -1) 
	{
		cout << height[i] << endl;
	}
	else
	{
		output(pre[i]);
		cout << height[i] << endl;
	}
}

int main()
{
	limit = 0;
	maxlen = -1;
	while(cin >> height[limit])
	{
		len[limit] = 1;
		pre[limit++] = -1;
	}
	limit--;
	for(i = 0;i < limit;i++)
	{
		for(j = i + 1;j <= limit;j++)
		{
			if(height[j] > height[i])
			{
				if(len[i] + 1 >= len[j])
				{
					len[j] = len[i] + 1;
					pre[j] = i;
					if(len[j] >= maxlen)
					{
						maxlen = len[j];
						tail = j;
					}
				}
			}
		}
	}
	
	cout << maxlen << endl << '-' << endl;

	output(tail);
	
	return 0;
}

[mohiul alam prince]

try for this input
2
-100000

after increase ur array size
int height[200005];
int len[200005];
int pre[200005];

MAP

[Morning]

yeah,that's why i got WA.
thank u so much!

[Ndiyaa ndako]

I am using the O(n log k) algorithm but I cannot get it accepted. Could you post some test cases?

[Moha]

I am getting WA, in this problem, can anybody post some tested testcases.
I use long long number but, still WA!
my code, answer adrian Testcase correctly, and i don't know where is my bug.
can anybody help me?

[sds1100]

#include <fstream.h>
int k,a[1000000],n,cnt,max,d[1000000],p[1000000];
void prs(int aa){
if(p[aa]==-1){
cout << a[aa] << endl;
return;
}
prs(p[aa]);
cout << a[aa] << endl;
}
void main()
{
int i,j;
while(cin >> k){
p[cnt]=-1;
a[cnt++]=k;
}
n=cnt;
d[0]=1;
int max=-999;
for(i=0;i<n;i++){
cnt=0;
for(j=0;j<i;j++){
if(a>a[j]){
if(d<=d[j]){
d=d[j]+1;
p=j;
}
}
}

if(d>max)max=d;
}
for(i=0;i<n;i++){
if(max==d)break;
}
cout << d << endl << "-" << endl;
prs(i);
}

[mf]

TLE -- because your program isn't fast enough. Generate an input with 100000 random numbers, and you'll see why.

You have to find a better algorithm, or use some clever data structure to speed up yours.

[sds1100]

Code: Select all

#include <fstream.h>
#include <memory.h>
#define MAX 200005
typedef long long int LLINT
LLINT a[MAX],x[MAX],t,n,now,p[MAX],*aa[MAX],aacnt[MAX],go[MAX],gocnt,aanow,anum[MAX];

void BoundCheck(int i)
{
	int *t;
	if (anum[i] == 0) {
		anum[i] = 20;
		aa[i] = new LLINT[20];
	}
	else if (anum[i] <= aacnt[i]) {		
		t = new LLINT[anum[i]*2];
		memcpy(t, aa[i], anum[i]*sizeof(int));
		delete [] aa[i];
		aa[i] = t;
		anum[i] <<= 1;
	}
}


void main()
{
	int i,j,sw=0;
	while(cin >> t){
		a[n]=-2147483648;
		x[n++]=t;
	}
	for(i=0;i<n;i++){
		sw=0;
		for(j=0;j<=now;j++){
			if(x[i]<=a[j]){
				a[j]=x[i];
				sw=1;				
				aacnt[j]++;				
				BoundCheck(j);
				aa[j][aacnt[j]]=x[i];
				break;
			}
		}
		if(sw==0){
			anum[now] = 8;
			aa[now] = new LLINT[8];
			if(aacnt[now]==0){
				aa[now][0]=x[i];
			}
			a[now++]=x[i];
		}
	}
	for(i=0;i<now;i++){
		aacnt[i]++;
	}
	cout << now << endl << "-" << endl;
	go[gocnt++]=aa[now-1][0];
	aanow=aa[now-1][0];
	for(i=now-2;i>=0;i--){
		for(j=0;j<aacnt[i];j++){
			if(aa[i][j]<aanow){
				go[gocnt++]=aa[i][j];
				aanow=aa[i][j];
				break;
			}
		}
	}
	for(i=now-1;i>=0;i--){
		delete [] aa[i];
		cout << go[i] << endl;
	}
}

help me!

[ayon]

my compiler says its in boundcheck() function. declare t as LLINT *t, not int *t.

[tmdrbs6584]

I got CE..
but why?
#include<iostream.h>
int n,cnt;
int a[100000],d[100000],pos[100000],path[100000];
int main(){
int i,j;
int q=0;
while(cin >> a[q]){
if(a[q]==-1) break;
q++;
}
int max=0,idx;
for(i=0;i<q;i++)
pos=-1;
for(i=0;i<q;i++){
d=1;
for(j=0;j<i;j++){
if(a>a[j] && d<d[j]+1){
d=d[j]+1;
pos=j;
}
}
if(max<d){
max=d;
idx=i;

}
}
path[cnt++]=idx;
while(pos[idx]!=-1){
path[cnt++]=pos[idx];
idx=pos[idx];
}
cout << q << endl << "-" << endl;
for(i=cnt-1;i>=0;i---)
cout << a[path] << endl;
n=cnt=0;
for(i=0;i<300;i++)
a=d[i]=pos[i]=path[i]=0;
return 0;
}

[sohel]

line 34 of your code:

Code: Select all

for(i=cnt-1;i>=0;i---) 

i---

[A1]

I think you are using O(n^2) algorithm of LIS to solve this, but in this problem n could be as big as 100000
so n^2 solution will get TLE.
Try to use n log(n) solution...

[serur]

Hello everyone!
I read in Halim's website the explanation of O(nlog(k)) algo for LIS,
it seems I have grasped the main idea(for I got AC 231-"Testing the Catcher"), but how to restore the LIS itself and even how to maintain the predecessor array- it is still a mystery for me...
Would you be so kind to explain what is the the crux?
Is this multiple input problem?
If you want to cast a glance on my code (which invariably gives WA, though behaves well for my own I/O ), I'll send it immediately.

Algoritmist website also very good for this problem, I thank them too
Thank you.