ALTARAY - Editorial

Can’t spot mistake…getting WA :cry:

https://www.codechef.com/viewsolution/9757999

public static void main(String arg[])
{
Scanner sc=new Scanner(System.in);
int t=sc.nextInt();
int n;
while(t>0)
{
n=sc.nextInt();
long[] a=new long[n];
for(int i=0;i<n;i++)
{
a[i]=sc.nextLong();
}
int[] b=new int[n];
b[n-1]=1;
for(int i=n-2;i>=0;i–)
{

if(a[i]*a[i+1]<0)
b[i]=b[i+1]+1;
else
b[i]=1;
}
for(int x : b)
System.out.printf("%d ",x);
System.out.println();
t–;
}
}
}

time limit is exceeding

plz help

https://www.codechef.com/viewsolution/9972627
this is my solution.it works fine with the test cases but its not getting accepted. pls help
thanks in advance.

I would like to thank you for the time you invest in making such nice post cause as I think it can be very helpful for many people who just wish to get as much information about this topic as possible.

when i am running this code it is showing correct output, but when i am submitting it, it is showing wrong answer. Here is the link to my solution:
https://www.codechef.com/viewsolution/10155565

#include <stdio.h>

int a[100002];

int sign(int);

int dp(long long int, long long int,long long int);

int main(void) {
long long int n,t,i,x;
scanf("%lld",&t);
while(t–)
{
scanf("%lld",&n);
for(i=0;i<n;i++)
scanf("%lld",&a[i]);

      for(i=0;i<n;i++)
          {
            x=dp(i,sign(a[i]),n);
            printf("%lld ",x);
          }
       printf("\n");
        
    }
// your code goes here
return 0;

}

int dp(long long int y,long long int s,long long int n)
{
if(y==n-1)
return 1;

    else if(sign(a[y+1])!=s)
     return  1+dp(y+1,sign(a[y+1]),n);

    else
     return 1;

}

int sign(int n)
{
if(n>0)
return 1;

  else
   return 0;

}

I am getting time limit exceeding but cant see my mistake , plz help

import java.io.*;

import java.math.*;

import java.util.*;

class subarrayprefix
{

public static Long[] a=new Long[1000000];

public static Long[] ans=new Long[1000000];
public static void main(String arg[])
{
	Scanner sc=new Scanner(System.in);
	int t=sc.nextInt();
	int n;
	long x=1;
	while(t>0)
	{
		n=sc.nextInt();
		for(int i=0;i<n;i++)
			a[i]=sc.nextLong();
		ans[n-1]=x;
		for(int i=n-2;i>=0;i--)
		{
			if((a[i+1]*a[i])<0)
				ans[i]=ans[i+1]+1;
			else
				ans[i]=x;
		}
		for(int i=0;i<n;i++)
			System.out.printf("%d ",ans[i]);
		System.out.println();
		t--;
	}
}

}

https://www.codechef.com/viewsolution/10533083
Can you check why am I getting a WA ?

This problem can be easily solved using stacks. Here is my solution Online Compiler and IDE >> C/C++, Java, PHP, Python, Perl and 70+ other compilers and interpreters - Ideone.com .
If you find anything incorrect please let me know.

#include
#include <stdio.h>
#include

int main() {

int cases, i;
scanf("%d", &cases);
for (i=0; i<cases; i++) {
	int n,j,k;
	long int a[100000];
	scanf("%d", &n);
	for (j=0; j<n; j++)
		std::cin>>a[j];
	for (j=0; j<n; j++) {
		int count=1;
		for (k=j; k<n; k++) {
		    //printf("%d and %d\n", a[k], a[k+1]);
			if (a[k]*a[k+1] < 0)
				count++;
			else
			    break;
		}
		printf("%d ", count);		
	}
	printf("\n");
}

return 0;

}

What is wrong in this code, Why is it showing Wrong Answer !

#include
using namespace std;

int main()
{
int t;
cin>>t;
while(t–)
{
int n;
cin>>n;
string s;
long long int x;
int a[n];
for(int i=0;i<n;i++)
{
cin>>x;
if(x>0)
s+=’+’;
else
s+=’-’;
a[i]=1;
}
//cout<<s<<endl;
for(int i=1;i<n;i++)
{
if(s[i]!=s[i-1])
a[0]++;
else
break;
}
cout<<a[0]<<" “;
for(int i=1;i<n;i++)
{
if(a[i-1]>1)
{
a[i]=a[i-1]-1;
}
else
for(int j=i+1;j<n;j++)
{
if(s[j]!=s[j-1])
a[i]++;
else
break;
}
cout<<a[i]<<” ";
}
cout<<endl;
}
return 0;
}

I am wondering if you could solve that problem using a segment tree ? Anyone used that approach ? Would it be more efficient ?

Thanks

One question we can ask in an interview will be to how to treat 0’s .

check out a very simple solution here
https://github.com/anjn98/codechef/blob/master/ALTARAY.cpp

#include<stdio.h>
#define MAX 1000007
typedef long long int ll;

int stk[MAX];
int top = -1;
 
int empty(){
 
    return top == -1;
}
 
void push(int x){
 
    stk[++top] = x;
}
 
int pop(){
 
    if(!empty())
        return stk[top--];
}
 
int peek(){
 
    if(!empty())
        return stk[top];
}
 
 
int main(int argc, char const *argv[])
{
    /* code */
    int t;
    scanf("%d",&t);
    
    while(t--){
 
        int n;
        scanf("%d",&n);
 
        int res[n],s[n];
        ll a[n];
        for(int i=0;i<n;i++){
 
            scanf("%lld",a+i);
            res[i] = 1;
            s[i] = (a[i]>0)? 1 : -1;
        }
 
        
        top=-1;
        int cnt=0;
        for(int i=0;i<n;i++){
 
            if(!empty() && (s[peek()] == s[i]) ){
 
                cnt=0;
                while(!empty()){
 
                    res[peek()] += cnt++;
                    pop();
                }
            }
            else
                push(i);
        }
 
        cnt=0;
        while(!empty()){
 
            res[peek()] += cnt++;
            pop();
        }
 
        for(int i=0;i<n;i++)
            printf("%d ",res[i]);
        
        printf("\n");
    }
    return 0;
}

I want to know on which test case this stack implementation fails…help…

could someone help why i am getting RTE here

def getAlt(arr):
n = len(arr)
ans = [1]*n
for i in range(n-2, -1, -1):
# print(ans[i], ans[i+1])
if (arr[i] < 0 and arr[i+1] > 0) or (arr[i] > 0 and arr[i+1] < 0):
ans[i] += ans[i+1]
# print(ans)
print(’ '.join(str(x) for x in ans))

for _ in range(int(input())):
    n = int(input())
    arr = list(map(int, input().split()))
    getAlt(arr)

A simple pytonh DP approach utilising the fact that minimum length will be taken as 1 per index

Why can’t we do this?

  1. Change every positive element to 1 and every negative element to -1
  2. Then calculate to product of every two consective terms of the new array
  3. Check the maximum number of continuous -1 's in the product array
  4. The answer is max number of -1 's (-1)
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There is something wrong in your claims. Can you give links of both the solutions?

@dpraveen

CodeChef: Practical coding for everyone ← this is solution where a is long long int(WA)
CodeChef: Practical coding for everyone ← this is the other one(AC)

The Above solutions are similar to solution in editorial

CodeChef: Practical coding for everyone ← This is the one I submitted during contest.(WA)

CodeChef: Practical coding for everyone ← This is with a is long long int (WA)

CodeChef: Practical coding for everyone ← This is the same submission with only one change as mentioned above in previous comment(i.e. including 1ll). (AC)

1 Like