A doubt in CENS20D

help
1

I have submitted two codes earlier for the problem Priya and And - CENS20D,

this code got WA 
for(int i=0;i<n;i++) {
	for(int j=i+1;j<n;j++) {
		if(a[i]&a[j]==a[i]) ans++;
	}
}
this code got AC 
for(int i=0;i<n;i++) {
	for(int j=0;j<n;j++) {
		if((a[i]&a[j])==a[i] and i<j) ans++;
	}
}

please check the links to the WA code and the AC code .

Thanks in advance :slight_smile:

2

Same thing happened to me. Very disappointing. I ended up with 2 WAs for no reason which worsened my rank.

3 Likes
3

Problem was with ( ) == a[i]
I also made the same mistake

4 Likes
4

its the brackets that’s giving you ac. (a[i] & a[j]) == a[i]

2 Likes
5

== has higher preference than & operator
That’s why you got WA in first code.

4 Likes
6

got it. operator precedence, my bad sorry ! :slight_smile:

1 Like
7

So what’s your question exactly ?
If you are asking that why second one got AC then its because (i<j) was given in question and you need to put the operands of bitwise &, in round brackets.

2 Likes
8

This is the reason you should turn on compiler warnings. I wrote the first code, and got a warning.

My Geany Compiler Flags are:

Compile (F8):
g++ -std=c++17 -Wshadow -Wall -o "%e" "%f" -O2 -Wno-unused-result

Build (F9):
g++ -std=c++17 -Wshadow -Wall -o "%e" "%f" -g -fsanitize=address -fsanitize=undefined -D_GLIBCXX_DEBUG

3 Likes
9

‘==’ is done first and then ‘&’. The problem is just with the brackets.

2 Likes
10

Yes but it worked for the samples. That is why I submitted the code in the first place.

2 Likes
11

In sample all the number were same in the array

3 Likes
12

Then can you explain why it worked for the sample test case?

1 Like
13

Just generate some test cases and check which ones have different output on the codes.

14

So it was intentionally done :no_mouth:

2 Likes
15

in the first sample all the numbers were the same and in the second one, you don’t get to the point of comparison

16

Read editorial, you’ll know better. :slightly_smiling_face:

1 Like
17

I guess so :upside_down_face:

18

I think first loop should be till n-1 and the brackets .
Do the dry run you will understand .
Ps: we are checking for pairs hence why should we check for last element ?

19

No, j has to be less than n

20

I said first loop brother :slight_smile: