10344 - 23 out of 5

[frankhuhu]

Hi! I need help for p10344.
I get WA,and I don't why.I think there should be 5!*3^4=9720 conditions.So Backtracking it.
Here is the code:

#include <iostream.h>
#include <string.h>

int oper[4];
int value[5];
bool flag;

int cal()
{
int result;
switch(oper[0]){
case 1:result=value[0]+value[1];break;
case 2:result=value[0]-value[1];break;
case 3:result=value[0]*value[1];break;
}
switch(oper[1]){
case 1:result=result+value[2];break;
case 2:result=result-value[2];break;
case 3:result=result*value[2];break;
}
switch(oper[2]){
case 1:result=result+value[3];break;
case 2:result=result-value[3];break;
case 3:result=result*value[3];break;
}
switch(oper[3]){
case 1:result=result+value[4];break;
case 2:result=result-value[4];break;
case 3:result=result*value[4];break;
}
return result;
}

void permOper(int index)
{
if (index==4)
{
if (cal()==23)
flag = true;
}
else
{
oper[index]++;
permOper(index+1);
oper[index]++;
permOper(index+1);
oper[index]++;
permOper(index+1);
oper[index] -= 3;
}

}

void permValue(int *p,const int k,int n)
{
if (k==n-1)
{
permOper(0);
}
else
{
int i;
for (i=k;i<n;i++)
{
int temp;
temp=p[k];p[k]=p;p=temp;
permValue(p,k+1,n);
temp=p[k];p[k]=p;p=temp;
}
}
}




int main()
{
while (cin>>value[0]>>value[1]>>value[2]>>value[3]>>value[4])
{
if (value[0]==0 && value[1]==0 && value[2]==0 && value[3]==0 && value[4]==0)
break;
memset(oper,0,sizeof(oper));
flag=false;
permValue(value,0,5);
if (flag)
cout<<"Possible"<<endl;
else
cout<<"Impossible"<<endl;
}
return 0;
}

Is there anyone can help me?
Thx in advance!!!

[epsilon0]

hello, i'm having trouble with this problem as well.

i use recursion, so i work things in reverse order from you. my code is much shorter too but i cant see where the problem is.

Code: Select all

#include <stdio.h>

int possible(int *t, int len, int res)
{
        int i, j, tmp;
        if (len == 1)
                return (*t == res);
        len--;
        for (i = 0; i <= len; i++)
        {
                tmp = t[0];
                for (j = 0; j < len; j++)
                        t[j] = t[j+1];
                t[len] = tmp;
                if (possible(t, len, res + t[len]))
                        return 1;
                if (possible(t, len, res - t[len]))
                        return 1;
                if ((t[len] && !(res % t[len]) && possible(t, len, res / t[len])
                    )   || (!t[len] && !res)            )
                        return 1;
        }
        return 0;
}

int main()
{
        int n[5];
        for (;;)
        {
                scanf("%d %d %d %d %d", n, n+1, n+2, n+3, n+4);
                if (!(n[0] || n[1] || n[2] || n[3] || n[4]))
                        break;
                printf("%s\n", possible(n, 5, 23) ? "Possible" : "Impossible");
        }
        return 0;
}

i'm probably missing something, but i dont see... are we allowed to have negative numbers as intermediary results!?

[frankhuhu]

Oh.My God!!
My friends told me that this problem might have been changed.His code used to get AC,but now get WA.Perhaps the test data have been changed and there maybe some mistakes in it.

[epsilon0]

i don't know if it's of any interest, but take a look at this case:

1 2 3 4 35
(((1 - 4) - 3) * 2) + 35 = 23

here you get negative numbers along the way. also, if you add the restriction that all results must be positive, then there is no solution.

unfortunately, i submitted the modified code and still got WA. so the problem must be something else

[epsilon0]

hello frankhuhu,

i have compiled your code and compared its output with mine or 10,000 random test cases.

both programs produce exactly the same output.

also i tested with 0's and they still behave the same.

i have also modified my code to print the operation (when possible) and check it, and found no error.

at this point i think it's most likely an error in the test cases of the judge as you mentionned.

[helloneo]

I got AC with a little modification of your code..
Just think of negative input or output..?
I don't know exactly why..

[frankhuhu]

Hi,helloneo!
You said there are negative inputs? But the problem says "The Input consists of 5-Tupels of positive Integers, each between 1 and 50."
If there are negative inputs,where should I modifiy my code?
I can not make it out,plz help me!!!

[epsilon0]

hey helloneo,

whose code did you modify? also what do you mean about negative i/o? i think the operators % and / work fine with negative integers...

can you post test cases where your output differs from ours to help us spot the problem? thanks.

[helloneo]

hey helloneo,

whose code did you modify? also what do you mean about negative i/o? i think the operators % and / work fine with negative integers...

can you post test cases where your output differs from ours to help us spot the problem? thanks.

i modified frankhuhu's code..

my test case is..

Code: Select all

32 31 1 5 8
0 0 0 0 0

my output is POSSIBLE
anybody could make 23 with those numbers..?

i still don't understand why..

maybe this way..?

( 32 - ( 1 * 5 * 8 ) ) + 31
or
(( 1 * 5 ) * - 8 ) + 32 + 31

[epsilon0]

you can't do that, those 2 expressions are not of the required form...

though, i modified my code accordingly and got AC.. but this is so wrong!

[Jeff]

Please help me.....thanks.....

Code: Select all

#include<stdio.h>
#include<string.h>
	int num[5];
	bool open[5];
	bool dfs(int now,int step)
	{
		int i;
		if(step==5)
		{
			if(now==23)
				return 1;
			return 0;
		}
		for(i=0;i<5;i++)
		{
			if(!open[i])
			{
				open[i]=1;
				if(dfs(now+num[i],step+1))
					return 1;
				if(dfs(now-num[i],step+1))
					return 1;
				if(dfs(now*num[i],step+1))
					return 1;
				open[i]=0;
			}
		}
		return 0;
	}
	int main()
	{
		int i;
		bool k;
		while(scanf("%d %d %d %d %d",&num[0],&num[1],&num[2],&num[3],&num[4])==5)
		{
			if(num[0]==0 && num[1]==0 && num[2]==0 && num[3]==0 && num[4]==0)
				return 0;
			memset(open,0,sizeof(open));
			k=0;
			for(i=0;i<5;i++)
			{
				open[i]=1;
				k=dfs(num[i],1);
				if(k)
					break;
				open[i]=0;
			}
			if(k)
				printf("Possible\n");
			else
				printf("Impossible\n");
		}
		return 0;
	}

[epsilon0]

i got your program accepted with just a little modification:

consider (x * -y) is a legal operation like + - and *

just a little comment on your coding style... you should REALLY chose between C and C++ they are 2 different languages.

[Jeff]

thank you very much~~~~

[Chok]

Hi Jeff and Epsilon
I'm getting WA several times. I didnt use dfs. At first i generate permutation and then check whether any of them is valid or not.
Here is my code. Please help. Thankx in advance.

Code: Select all

#include<stdio.h>
#include<math.h>
#include<string.h>


#define MAX 5

int flag,np;
int a[MAX];
int b[MAX];
int dic[121][MAX];
int com[MAX];


void swap(int *x,int *y)
{
	int tmp=*x;
	*x=*y;
	*y=tmp;
}

void perm(int pos)
{
	int i,k;
	if(pos==5)
	{
		for(k=0;k<5;k++)
			dic[np][k]=a[k];
		np++;
		return;
	}
	for(i=pos;i<5;i++)
	{
		swap(&a[pos],&a[i]);
		perm(pos+1);
		swap(&a[pos],&a[i]);		
	}
	return;
}


int back(int i,int s)
{
	if(i==5)
	{
		if(s==23)
		{
			printf("Possible\n");
			flag=1;
			return 1;
		}
		else
			return 0;
	}
	if(back(i+1,s)==1)
		return 1;
	if(back(i+1,s*b[i])==1)
		return 1;
	if(back(i+1,s+b[i])==1)
		return 1;	
	if(back(i+1,s-b[i])==1)
		return 1;	
	return 0;
}

int main()
{
	int i,j;
	//freopen("10344.in","r",stdin);
	//freopen("10344.out","w",stdout);
	while(scanf("%d %d %d %d %d",&a[0],&a[1],&a[2],&a[3],&a[4]),a[0] || a[1] || a[2] || a[3] || a[1])
	{
		flag=0;
		np=0;
		memset(dic,0,sizeof(dic));
		perm(0);
		for(i=0;i<np;i++)
		{
			for(j=0;j<5;j++)
				b[j]=dic[i][j];
			back(0,0);
			if(flag)
				break;
		}
		if(!flag)
			printf("Impossible\n");
	}
	return 0;
}

[I LIKE GN]

hello...
my program gives expected output for all the i/o's posted in the board but
i get WA...
so please give me some more
i use division when integer division is possible (i.e. there is no remainder after the division)
also i use recursion to generate all permutation...
i amm not getting what's wrong.
please help.