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Vytlačte prvých n čísel s presne dvoma nastavenými bitmi

Dané číslo n vytlačí prvých n kladných celých čísel s presne dvoma nastavenými bitmi v ich binárnej reprezentácii.
Príklady: 

Input: n = 3  
Output: 3 5 6  
The first 3 numbers with two set bits are 3 (0011)  
5 (0101) and 6 (0110)  
Input: n = 5  
Output: 3 5 6 9 10 12

A Jednoduché riešenie je zvážiť všetky kladné celé čísla po jednom od 1. Pre každé číslo skontrolujte, či má práve dve sady bitov. Ak má číslo presne dva nastavené bity, vytlačte ho a zvýšte počet takýchto čísel.
An Efektívne riešenie je priamo generovať takéto čísla. Ak jasne dodržíme čísla, môžeme ich prepísať tak, ako je uvedené nižšie pow(21)+pow(20) pow(22)+pow(20) pow(22)+pow(21) pow(23)+pow(20) pow(23)+pow(21) pow(23)+pow(22) .........
Všetky čísla môžu byť generované v rastúcom poradí podľa vyššieho z dvoch nastavených bitov. Cieľom je opraviť vyššie z dvoch bitov jeden po druhom. Pre aktuálny vyšší nastavený bit zvážte všetky nižšie bity a vytlačte vytvorené čísla.



C++ 
// C++ program to print first n numbers // with exactly two set bits #include    using namespace std; // Prints first n numbers with two set bits void printTwoSetBitNums(int n) {  // Initialize higher of two sets bits  int x = 1;  // Keep reducing n for every number  // with two set bits.  while (n > 0)  {  // Consider all lower set bits for  // current higher set bit  int y = 0;  while (y < x)  {  // Print current number  cout << (1 << x) + (1 << y) << ' ';  // If we have found n numbers  n--;  if (n == 0)  return;  // Consider next lower bit for current  // higher bit.  y++;  }  // Increment higher set bit  x++;  } } // Driver code int main() {  printTwoSetBitNums(4);  return 0; }
Java 
// Java program to print first n numbers // with exactly two set bits import java.io.*; class GFG  {  // Function to print first n numbers with two set bits  static void printTwoSetBitNums(int n)  {  // Initialize higher of two sets bits  int x = 1;    // Keep reducing n for every number  // with two set bits  while (n > 0)  {  // Consider all lower set bits for  // current higher set bit  int y = 0;  while (y < x)  {  // Print current number  System.out.print(((1 << x) + (1 << y)) +' ');    // If we have found n numbers  n--;  if (n == 0)  return;    // Consider next lower bit for current  // higher bit.  y++;  }    // Increment higher set bit  x++;  }  }    // Driver program  public static void main (String[] args)   {  int n = 4;  printTwoSetBitNums(n);  } } // This code is contributed by Pramod Kumar
Python3 
# Python3 program to print first n  # numbers with exactly two set bits  # Prints first n numbers  # with two set bits  def printTwoSetBitNums(n) : # Initialize higher of # two sets bits  x = 1 # Keep reducing n for every  # number with two set bits.  while (n > 0) : # Consider all lower set bits  # for current higher set bit  y = 0 while (y < x) : # Print current number  print((1 << x) + (1 << y) end = ' ' ) # If we have found n numbers  n -= 1 if (n == 0) : return # Consider next lower bit  # for current higher bit.  y += 1 # Increment higher set bit  x += 1 # Driver code  printTwoSetBitNums(4) # This code is contributed  # by Smitha
C# 
// C# program to print first n numbers // with exactly two set bits using System; class GFG   {    // Function to print first n  // numbers with two set bits  static void printTwoSetBitNums(int n)  {    // Initialize higher of   // two sets bits  int x = 1;    // Keep reducing n for every  // number with two set bits  while (n > 0)  {    // Consider all lower set bits   // for current higher set bit  int y = 0;  while (y < x)  {    // Print current number  Console.Write(((1 << x) +  (1 << y)) +' ');    // If we have found n numbers  n--;  if (n == 0)  return;    // Consider next lower bit   // for current higher bit.  y++;  }    // Increment higher set bit  x++;  }  }    // Driver program  public static void Main()   {  int n = 4;  printTwoSetBitNums(n);  } }   // This code is contributed by Anant Agarwal.
JavaScript 
<script> // Javascript program to print first n numbers // with exactly two set bits // Prints first n numbers with two set bits function printTwoSetBitNums(n) {  // Initialize higher of two sets bits  let x = 1;  // Keep reducing n for every number  // with two set bits.  while (n > 0)  {    // Consider all lower set bits for  // current higher set bit  let y = 0;  while (y < x)  {    // Print current number  document.write((1 << x) + (1 << y) + ' ');  // If we have found n numbers  n--;  if (n == 0)  return;  // Consider next lower bit for current  // higher bit.  y++;  }  // Increment higher set bit  x++;  } } // Driver code printTwoSetBitNums(4); // This code is contributed by Mayank Tyagi </script>
PHP 
 // PHP program to print  // first n numbers with  // exactly two set bits // Prints first n numbers  // with two set bits function printTwoSetBitNums($n) { // Initialize higher of // two sets bits $x = 1; // Keep reducing n for  // every number with  // two set bits. while ($n > 0) { // Consider all lower set  // bits for current higher  // set bit $y = 0; while ($y < $x) { // Print current number echo (1 << $x) + (1 << $y) ' '; // If we have found n numbers $n--; if ($n == 0) return; // Consider next lower  // bit for current  // higher bit. $y++; } // Increment higher set bit $x++; } } // Driver code printTwoSetBitNums(4); // This code is contributed by Ajit ?>

výstup:  
 

bfs vs dfs 
3 5 6 9


Časová zložitosť: O(n)

int zdvojnásobiť

Pomocný priestor: O(1)



Prístup č. 2: Použite while a pripojte sa


Prístup je začať od celého čísla 3 a skontrolovať, či sa počet nastavených bitov v jeho binárnej reprezentácii rovná 2 alebo nie. Ak má presne 2 nastavené bity, pridajte ho do zoznamu čísel s 2 nastavenými bitmi, kým zoznam nebude mať n prvkov.

Algoritmus

1. Inicializujte prázdny zoznam res na uloženie celých čísel s presne dvoma nastavenými bitmi.
2. Inicializujte celočíselnú premennú i na 3.
3. Kým je dĺžka zoznamu res menšia ako n, urobte nasledovné:
a. Pomocou metódy count() reťazca skontrolujte, či sa počet nastavených bitov v binárnej reprezentácii i rovná 2 alebo nie.
b. Ak je počet nastavených bitov rovný 2, potom pridajte i do zoznamu res.
c. Zvýšenie i o 1.
4. Vráťte zoznam resp.

C++ 
#include    #include  using namespace std; int countSetBits(int num) {  int count = 0;  while (num > 0) {  count += num & 1;  num >>= 1;  }  return count; } vector<int> numbersWithTwoSetBits(int n) {  vector<int> res;  int i = 3;  while (res.size() < n) {  if (countSetBits(i) == 2) {  res.push_back(i);  }  i++;  }  return res; } int main() {  int n = 3;  vector<int> result = numbersWithTwoSetBits(n);  cout << 'Result: ';  for (int i = 0; i < result.size(); i++) {  cout << result[i] << ' ';  }  cout << endl;  return 0; }
Java 
// Java program for the above approach import java.util.ArrayList; import java.util.List; public class GFG {  // Function to count the number of set bits (binary 1s)  // in an integer  static int countSetBits(int num)  {  int count = 0;  while (num > 0) {  count += num & 1; // Increment count if the last  // bit is set (1)  num >>= 1; // Right shift to check the next bit  }  return count;  }  // Function to generate 'n' numbers with exactly two set  // bits in their binary representation  static List<Integer> numbersWithTwoSetBits(int n)  {  List<Integer> res = new ArrayList<>();  int i = 3; // Start from 3 as the first number with  // two set bits  while (res.size() < n) {  if (countSetBits(i)  == 2) { // Check if the number has exactly  // two set bits  res.add(  i); // Add the number to the result list  }  i++; // Move to the next number  }  return res;  }  public static void main(String[] args)  {  int n = 3; // Number of numbers with two set bits to  // generate  List<Integer> result = numbersWithTwoSetBits(  n); // Get the generated numbers  for (int num : result) {  System.out.print(  num + ' '); // Display the generated numbers  }  System.out.println();  } } // This code is contributed by Susobhan Akhuli
Python3 
def numbersWithTwoSetBits(n): res = [] i = 3 while len(res) < n: if bin(i).count('1') == 2: res.append(i) i += 1 return res n = 3 result = numbersWithTwoSetBits(n) output_string = ' '.join(str(x) for x in result) print(output_string)
C# 
using System; using System.Collections.Generic; class Program {  // Function to count the number of set bits (binary 1s) in an integer  static int CountSetBits(int num)  {  int count = 0;  while (num > 0)  {  count += num & 1; // Increment count if the last bit is set (1)  num >>= 1; // Right shift to check the next bit  }  return count;  }  // Function to generate 'n' numbers with exactly two set bits in their binary representation  static List<int> NumbersWithTwoSetBits(int n)  {  List<int> res = new List<int>();  int i = 3; // Start from 3 as the first number with two set bits  while (res.Count < n)  {  if (CountSetBits(i) == 2) // Check if the number has exactly two set bits  {  res.Add(i); // Add the number to the result list  }  i++; // Move to the next number  }  return res;  }  static void Main(string[] args)  {  int n = 3; // Number of numbers with two set bits to generate  List<int> result = NumbersWithTwoSetBits(n); // Get the generated numbers  Console.Write('Result: ');  foreach (int num in result)  {  Console.Write(num + ' '); // Display the generated numbers  }  Console.WriteLine();  } }
JavaScript 
// Javascript program for the above approach // Function to count the number of set bits (binary 1s) // in an integer function countSetBits(num) {  let count = 0;  while (num > 0) {  count += num & 1; // Increment count if the last  // bit is set (1)  num >>= 1; // Right shift to check the next bit  }  return count; } // Function to generate 'n' numbers with exactly two set // bits in their binary representation function numbersWithTwoSetBits(n) {  let res = [];  let i = 3; // Start from 3 as the first number with  // two set bits  while (res.length < n) {  if (countSetBits(i) === 2) { // Check if the number has exactly  // two set bits  res.push(i); // Add the number to the result list  }  i++; // Move to the next number  }  return res; } // Number of numbers with two set bits to generate let n = 3; // Get the generated numbers let result = numbersWithTwoSetBits(n); // Display the generated numbers console.log(result.join(' ')); // This code is contributed by Susobhan Akhuli

Výstup 
3 5 6

Časová zložitosť: O(n log n), kde n je počet celých čísel s presne dvoma nastavenými bitmi. Je to preto, že kontrolujeme počet nastavených bitov v binárnej reprezentácii každého celého čísla, čo trvá O(log n) čas.



Priestorová zložitosť: O(n) kde n je počet celých čísel s presne dvoma nastavenými bitmi. Je to preto, že v pamäti ukladáme zoznam celých čísel s dvoma nastavenými bitmi.
 

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