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BitMask

Posted
By So Hee Park 1 min read

✅ BitMask

modify numbers into binary representaion
Bit: binary digit, smallest unit for computer

✅ Code

✔️ present in array

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//array
int[] array1 = [1, 1, 1, 1, 0];
int[] array2 = [1, 1, 0, 1, 0];
int[] array3 = [1, 0, 1, 0, 0];

✔️ present in bitmask

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//bitmask
{ 0, 1, 2, 3, 4 } => 11111 = 16 + 8 + 4 + 2 + 1 = 31
{ 1, 2, 3, 4 } => 11110
{ 1, 2, 4 } => 10110
{ 2, 4 } => 10100 = 16 + 4 = 20
{ 1 } => 00010

✔️ modify binary back to decimal

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//into decimal
{ 0, 1, 2, 3, 4 } => 11111
{ 1, 2, 3, 4 } => 11110
{ 1, 2, 4 } => 10110
{ 2, 4 } => 10100
{ 1 } => 00010

✔️ Caculators

  • AND
  • OR
  • NOT ~ ~1010 = 0101

  • Shift «, » 00001010 << 2 = 101000
    00001010 >> 2 = 000010 

    ✔️ change 0 to 1

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//1010
//change i=2 to 1

1010 | 1 << 2
//1 << 2 = 100
1010 | 0100 => 1110

✔️ change 1 to 0

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1110 & ~1 << 2
// ~1 = 1110
// 1110 << 2 = 1011
1110 & 1011 => 1010

💡 Reference

https://mygumi.tistory.com/361

Coding Test, Algorithm
This post is licensed under CC BY 4.0 by the author.