Doubt on leetcode probelem

#1

my code=https://ide.codingblocks.com/s/474842

Why did not my code work.
I saw the discussins and find out the correct approach=

In the correct approach why have they used j<22
pplz explain

#2

hello @Somasree

please share the question link with me

#3

Sorry
problem link-https://leetcode.com/problems/count-good-meals/

#4

…

all u r checking is whether the total sum is even or not.
but not all even number can be a represented as power of 2. for example-> 14 u cant represrent this as power of two.

look at the constraints they have said that maximum value of delicioness can be 2^20. so if u add two such number then u may get total sum upto 2^21.

that is the reason why they are iterating till j < 22 (ie j<=21) , to generate all power of 2 (from 2^0 to 2^21)

#5

ok thanku so much :grinning:

#6

In the code how the beow lines are ensuring that the only those nos are taken which sum upto any power of 4
m[s-a[i]];
s=s*2;

#7

…

note s. s is only having power of 2 right? becuase we are always multiplying s by 2 . so initially it will be 1 then 2 then 2^2 then 2^3 then 2^4 so on.

now

look at this line. here a[i] is the current element and we want to form s. that means another number that we are needed is s-a[i]
that is why we are using m[s-a[i]] this will give how many times number (s-a[i]) occured

#8

thank u so much :grinning:

#9

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