查找可以用给定数字形成的最大数字

给定一个整数arr []数组，表示一个数字。任务是编写一个程序，以使用这些数字生成最大数量的数字。
注意：数组中的数字在0到9之间。即0 例子：

Input : arr[] = {4, 7, 9, 2, 3}
Output : Largest number: 97432 

Input : arr[] = {8, 6, 0, 4, 6, 4, 2, 7}
Output : Largest number: 87664420 

天真的方法：天真的方法是按降序对给定的数字数组进行排序，然后使用数组中的数字形成数字，并保持数字顺序与排序后的数组相同。
时间复杂度：O(N logN)，其中N是位数。
下面是上述想法的实现：

C++

// C++ program to generate largest possible
// number with given digits
#include 
 
using namespace std;
 
// Function to generate largest possible
// number with given digits
int findMaxNum(int arr[], int n)
{  
    // sort the given array in
    // descending order
    sort(arr, arr+n, greater());
     
    int num = arr[0];
     
    // generate the number
    for(int i=1; i

---

Java

// Java program to generate largest
// possible number with given digits
import java.*;
import java.util.Arrays;
 
class GFG
{
// Function to generate largest
// possible number with given digits
static int findMaxNum(int arr[], int n)
{
    // sort the given array in
    // ascending order and then
    // traverse into descending
    Arrays.sort(arr);
     
    int num = arr[0];
     
    // generate the number
    for(int i = n - 1; i >= 0; i--)
    {
        num = num * 10 + arr[i];
    }
     
    return num;
}
 
// Driver code
public static void main(String[] args)
{
    int arr[] = {1, 2, 3, 4, 5, 0};
     
    int n = arr.length;
     
    System.out.println(findMaxNum(arr, n));
}
}
 
// This code is contributed by mits

Python3

# Python3 program to generate largest possible
# number with given digits
 
# Function to generate largest possible
# number with given digits
def findMaxNum(arr,n) :
 
    # sort the given array in
    # descending order
    arr.sort(reverse = True)
 
    # initialize num with starting
    # element of an arr
    num = arr[0]
 
    # generate the number
    for i in range(1,n) :
        num = num * 10 + arr[i]
 
    return num
 
# Driver code
if __name__ == "__main__" :
     
    arr = [1,2,3,4,5,0]
 
    n = len(arr)
 
    print(findMaxNum(arr,n))

C#

// C#  program to generate largest
// possible number with given digits
using System;
 
public class GFG{
    // Function to generate largest
// possible number with given digits
static int findMaxNum(int []arr, int n)
{
    // sort the given array in
    // ascending order and then
    // traverse into descending
    Array.Sort(arr);
     
    int num = arr[0];
     
    // generate the number
    for(int i = n - 1; i >= 0; i--)
    {
        num = num * 10 + arr[i];
    }
     
    return num;
}
 
// Driver code
    static public void Main (){
    int []arr = {1, 2, 3, 4, 5, 0};
    int n = arr.Length;
    Console.WriteLine(findMaxNum(arr, n));
}
}
 
// This code is contributed by Sachin..

Javascript

 
// Javascript program to generate largest possible
// number with given digits
 
// Function to generate largest possible
// number with given digits
function findMaxNum(arr, n)
{
    // sort the given array in
    // descending order
    arr.sort(function(a,b){return b-a;});
     
    var num = arr[0];
     
    // generate the number
    for(var i=1; i<n; i++)
    {
        num = num*10 + arr[i];
    }
     
    return num;
}
 
// Driver code
var arr = [1, 2, 3, 4, 5, 0];
 
var n = arr.length;
 
document.write(findMaxNum(arr,n));
 

---

输出：

543210

有效的方法：一种有效的方法是观察我们必须仅使用0到9之间的数字来形成数字。因此，我们可以创建一个大小为10的哈希表，以将给定数组中数字出现的次数存储到哈希表中。哈希表中的键将是0到9之间的数字，其值将是它们在数组中出现的次数。
最后，从数字9开始按降序打印数字。
下面是上述方法的实现：

C++

// C++ program to generate largest possible
// number with given digits
#include 
 
using namespace std;
 
// Function to generate largest possible
// number with given digits
void findMaxNum(int arr[], int n)
{  
    // Declare a hash array of size 10
    // and initialize all the elements to zero
    int hash[10] = {0};
     
    // store the number of occurrences of the digits
    // in the given array into the hash table
    for(int i=0; i=0; i--)
    {
        // Print the number of times a digits occurs
        for(int j=0; j

Java

// Java program to generate
// largest possible number
// with given digits
class GFG
{
 
// Function to generate
// largest possible number
// with given digits
static void findMaxNum(int arr[],
                       int n)
{
// Declare a hash array of
// size 10 and initialize
// all the elements to zero
int []hash = new int[10];
 
// store the number of occurrences
// of the digits in the given array
// into the hash table
for(int i = 0; i < n; i++)
{
    hash[arr[i]]++;
}
 
// Traverse the hash in descending
// order to print the required number
for(int i = 9; i >= 0; i--)
{
    // Print the number of
    // times a digits occurs
    for(int j = 0; j < hash[i]; j++)
        System.out.print(i);
}
}
 
// Driver code
public static void main(String[] args)
{
    int arr[] = {1, 2, 3, 4, 5, 0};
     
    int n = arr.length;
     
    findMaxNum(arr,n);
}
}
 
// This code is contributed
// by ChitraNayal

的Python 3

# Python 3 program to generate
# largest possible number
# with given digits
 
# Function to generate
# largest possible number
# with given digits
def findMaxNum(arr, n):
     
    # Declare a hash array of
    # size 10 and initialize
    # all the elements to zero
    hash = [0] * 10
     
    # store the number of occurrences
    # of the digits in the given array
    # into the hash table
    for i in range(n):
        hash[arr[i]] += 1
     
    # Traverse the hash in
    # descending order to
    # print the required number
    for i in range(9, -1, -1):
         
        # Print the number of
        # times a digits occurs
        for j in range(hash[i]):
            print(i, end = "")
 
# Driver code
if __name__ == "__main__":        
    arr = [1, 2, 3, 4, 5, 0]
    n =len(arr)
    findMaxNum(arr,n)
 
# This code is contributed
# by ChitraNayal

C＃

// C# program to generate
// largest possible number
// with given digits
using System;
 
class GFG
{
 
// Function to generate
// largest possible number
// with given digits
static void findMaxNum(int[] arr,
                       int n)
{
// Declare a hash array of
// size 10 and initialize
// all the elements to zero
int[] hash = new int[10];
 
// store the number of
// occurrences of the
// digits in the given
// array into the hash table
for(int i = 0; i < n; i++)
{
    hash[arr[i]]++;
}
 
// Traverse the hash in
// descending order to
// print the required number
for(int i = 9; i >= 0; i--)
{
    // Print the number of
    // times a digits occurs
    for(int j = 0; j < hash[i]; j++)
        Console.Write(i);
}
}
 
// Driver code
public static void Main()
{
    int[] arr = {1, 2, 3, 4, 5, 0};
     
    int n = arr.Length;
     
    findMaxNum(arr,n);
}
}
 
// This code is contributed
// by ChitraNayal

的PHP

= 0; $i--)
     
        // Print the number of
        // times a digits occurs
        for($j = 0; $j < $hash[$i]; $j++)
            echo $i;
}
 
// Driver code
$arr = array(1, 2, 3, 4, 5, 0);
$n = sizeof($arr);
findMaxNum($arr,$n);
 
// This code is contributed
// by mits
?>

Java脚本

 
// Javascript program to generate largest possible
// number with given digits
 
// Function to generate largest possible
// number with given digits
function findMaxNum( arr, n)
{
    // Declare a hash array of size 10
    // and initialize all the elements to zero
    var hash = Array(10).fill(0);
     
    // store the number of occurrences of the digits
    // in the given array into the hash table
    for(var i=0; i<n; i++)
    {
        hash[arr[i]]++;
    }
     
    // Traverse the hash in descending order
    // to print the required number
    for(var i=9; i>=0; i--)
    {
        // Print the number of times a digits occurs
        for(var j=0; j<hash[i]; j++)
            document.write(i);
    }
}
 
// Driver code
var arr = [1, 2, 3, 4, 5, 0];
 
var n = arr.length;
 
findMaxNum(arr,n);
 

输出：

543210

时间复杂度：O(N)，其中N是位数。
辅助空间：O(1)，哈希大小仅为10，这是一个常数。