给定两个数字N和K。任务是打印K个2的幂,并且它们的和为N。如果不可能,则打印-1。
例子:
Input: N = 9, K = 4
Output: 4 2 2 1
4 + 2 + 2 + 1 = 9
Input: N = 4, K = 5
Output: -1
方法:可以使用以下算法解决上述问题:
- 如果K小于N中的设置位数或大于N,则不可能。
- 将2的幂在设置的位插入优先级队列。
- 在优先级队列中进行迭代,直到获得K个元素, pop()最顶部的元素以及
- 推()
element / 2两次进入优先级队列。
- 一旦达到K个元素,就将它们打印出来。
下面是上述方法的实现:
C++
// CPP program to find k numbers that
// are power of 2 and have sum equal
// to N
#include
using namespace std;
// function to print numbers
void printNum(int n, int k)
{
// Count the number of set bits
int x = __builtin_popcount(n);
// Not-possible condition
if (k < x || k > n) {
cout << "-1";
return;
}
// Stores the number
priority_queue pq;
// Get the set bits
int two = 1;
while (n) {
if (n & 1) {
pq.push(two);
}
two = two * 2;
n = n >> 1;
}
// Iterate till we get K elements
while (pq.size() < k) {
// Get the topmost element
int el = pq.top();
pq.pop();
// Push the elements/2 into
// priority queue
pq.push(el / 2);
pq.push(el / 2);
}
// Print all elements
int ind = 0;
while (ind < k) {
cout << pq.top() << " ";
pq.pop();
ind++;
}
}
// Driver Code
int main()
{
int n = 9, k = 4;
printNum(n, k);
return 0;
}
Java
// Java program to find k numbers that
// are power of 2 and have sum equal
// to N
import java.io.*;
import java.util.*;
class GFG
{
// function to print numbers
static void printNum(int n, int k)
{
// Count the number of set bits
String str = Integer.toBinaryString(n);
int x = 0;
for (int i = 0; i < str.length(); i++)
if (str.charAt(i) == '1')
x++;
// Not-possible condition
if (k < x || k > n)
{
System.out.println("-1");
return;
}
// Stores the number
PriorityQueue pq =
new PriorityQueue<>(Comparator.reverseOrder());
// Get the set bits
int two = 1;
while (n > 0)
{
if ((n & 1) == 1)
pq.add(two);
two *= 2;
n = n >> 1;
}
// Iterate till we get K elements
while (pq.size() < k)
{
// Get the topmost element
int el = pq.poll();
// Push the elements/2 into
// priority queue
pq.add(el / 2);
pq.add(el / 2);
}
// Print all elements
int ind = 0;
while (ind < k)
{
System.out.print(pq.poll() + " ");
ind++;
}
}
// Driver Code
public static void main(String[] args)
{
int n = 9, k = 4;
printNum(n, k);
}
}
// This code is contributed by
// sanjeev2552
Python
# Python program to find k numbers that
# are power of 2 and have sum equal
# to N
# function to prnumbers
def printNum(n, k):
# Count the number of set bits
x = 0
m = n
while (m):
x += m & 1
m >>= 1
# Not-possible condition
if k < x or k > n:
print("-1")
return
# Stores the number
pq = []
# Get the set bits
two = 1
while (n):
if (n & 1):
pq.append(two)
two = two * 2
n = n >> 1
# Iterate till we get K elements
while (len(pq) < k):
# Get the topmost element
el = pq[-1]
pq.pop()
# append the elements/2 into
# priority queue
pq.append(el // 2)
pq.append(el // 2)
# Prall elements
ind = 0
pq.sort()
while (ind < k):
print(pq[-1], end = " ")
pq.pop()
ind += 1
# Driver Code
n = 9
k = 4
printNum(n, k)
# This code is contributed by SHUBHAMSINGH10
输出:
4 2 2 1
将n表示为两个|的正好k次幂之和。套装2
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