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__LOOSER__'s blog

By __LOOSER__, history, 2 years ago,

Hello ,

lets start from a basic question that can be solved using Binary number's Knowledge.

Basically in above question you are given n number of poison bottle, and t number of trial you can do ,how many minimum pig you need to find the bottle with poison.

Solution using Binary number knowledge

Trick 1

We can Hash any string to bit mask .

Lets start with simple example :-

Count number of different char in string

Using set
Using BitMask

We can use this trick to reduce the constant factor of 26 in many different kind of problem.

lets take a example

Leetcode Maximum Product of Word Lengths

Video Editorial

If you will try to solve this question using boolean array the time complexity will be O(n*n*26) that will lead to tle but you can improve time complexty to O(n*n) just by using bitmask

Soution Using BitMask

Trick 2

Printing all subset of K

What do I mean by subset

let say we have number whose binary representation is 1011 then we keep 0 as it is and we can make 1 to 0 or can keep 1.

Subsets of 1011 are 0011 , 1010 , 1011 and so on . 1100 is not subset because we will keep zero at place of zero.

so how many total number of subset will be there for any number

Answer

Now First question is How to generate all possible subset

void generate(int k) {
int num = k;
while (k) {
cout << k << " ";
k--;
k = k & num;
}
cout << 0 << '\n';
}


There are Many Question you can solve using this trick . SOS dp also uses this trick Sos Dp.

Lets see some Question:-

Leetcode Number of Valid Words for Each Puzzle

My Solution of above Question

Some Questions To Practice :

CodeChef Chef and Deque

Trick 3

Reducing Time Complexy By factor of B (Depend on your system) Using bitset

Errichto has video on same topic you can watch that

Errichto Video

Practice Question

Codechef Functional Array

Ok now discuss some of Important things related to Bits

--> Gray Code , normaly gray codes are used to check error while sending signals from one place to other place . Gray Code has special property that every consecutive number has atmost one digit different.

Binary Number to gray Code
Gray Code to Binary Number

--> We can find Minimum XOR of two element in array Just by sorting the array and taking minimum of xor of neighbouring element.

--> To find Maximum XOR of two element We can use trie data structre.

--> We can use Bit mask to solve problems related to "The Inclusion-Exclusion Principle" CP Algorithm Turorial

--> Few Equations Related To Bit Manipulation link

My YouTube Channel :- YouTube

• +8

By __LOOSER__, history, 2 years ago,

Hello Codeforces , I am lokesh , electrical engineer , mnnit , allahabad . It's almost 1.5 year I am doing codeforces . I learnt lots of new things . Now Its my duty to provide somethings to cp community . I am not too good at cp . I am starting a youtube channel on which I am going to upload videoes related to interviews as well as editorial of last 2-3 questions of div 3 if I could able to solve them in contest . As well as I will upload some stories related to my failure in 7 interview during my internship session .

For now I am learning some edition stuff you can subsribe my channel I will upload videoes soon.

my youtube channel

https://www.youtube.com/channel/UCHCGL-xmIy_Hm7fjfG697Bg

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