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Vibhor Singh
Vibhor Singh

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Flipping Bits Problem

#javascript #hackerrank #programming #beginners

This problem asks the solver to print the flipped bits of 32bit unsigned integer.

In detail, you would be provided an integer -

9 (base 10)

You have to write a function such that it returns the 32 bit unsigned decimal integer result -

4294967286 (base 10)

All code would be in Javascript but you can use any language to solve this problem.

How one goes from 9 to 4294967286?

  • first take the input and convert it a string using toString() function 
 let s=n.toString(2);
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  • initialize a new variable and assign it to 32-(length of string) 
 let temp=32-s.length;
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Why temp is equal to 32-s.length - variable s stores the number in binary format i.e. n=9 in decimal and s would store "1001" in binary {datatype of s is string here}, you are asked in this case to generate a 32 bit integer so to add the remaining bits in s, we assign temp to the given formula.

  • initialize a new variable and assign it to an empty string 
let temp_s="";
for(let i=0;i<temp;i++)
    temp_s+="0";
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temp_s appends 0 to an empty string of length temp.

  • res_s would hold the string full of 0 and the converted string of the number in binary format 
let res_s=temp_s+s;
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res_s=00000000000000000000000000001001

  • flip_s would store the flipped string as 1 would convert to 0 and 0 to 1 
let flip_s="";
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  • we use for of loop to traverse through string res_s 
for(let i of res_s) {
        if(i==="0")
            flip_s+="1";
        else if(i==="1")
            flip_s+="0";
    }
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Here every element in the string is checked for 0 and 1 and assigned to 1 and 0 respectively.

flip_s=11111111111111111111111111110110

  • print the value of given expression on console/prompt screen 
console.log( parseInt(flip_s, 2));
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Here, parseInt() method converts the flip_s variable to decimal form and output results in

4294967286

This problem is the part of HackerRank's 1 Month Interview Prep Kit.

Top comments (1)

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danyglez94 profile image
Daniel Gonzalez •

Thank you! You gave me the main idea, and I ended up coding this, I think is easier to understand it like this.

function flippingBits(n) {
  const binaryString = n.toString(2).padStart(32, "0");
  const flippedString = binaryString
    .split("")
    .map((bit) => (bit === "0" ? "1" : "0"))
    .join("");
  const flippedNumber = parseInt(flippedString, 2);
  return flippedNumber;
}
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