Given an array **arr[]** consisting of **N** integers which are either **0** or **7**, the task is to find the largest number that can be formed using the array elements such that it is divisible by **50**.

**Examples:**

Input:arr[] = {7, 7, 7, 7, 7, 7, 0, 0, 0, 0, 0, 0, 0}Output:777770000000

Input:arr[] = {7, 0}Output:0

**Naive Approach:** The simplest approach to solve this problem is based on the following observations:

- Visualizing
**50**to be equal to**5 * 10**, therefore any trailing zeros inserted will be divided by**10**present as a factor of**50**. Therefore, the task reduces to combining**7**s such that they are divisible by**5**and for a number to be divisible by**5**, its unit place should either be**0**or**5**.**Time Complexity:**O(2^{N})**Auxiliary Space:**O(1)

**Efficient Approach: **To optimize the above approach, the idea is to calculate the frequency of **7**s and **0**s present in the array and generate the required number which is divisible by **50**. Follow the steps below to solve the problem:

- Count the number of
**7**s and**0**s present in the array. - Calculate the
**nearest factor of 5**to the count of**7**s present in the array (as**35**is the smallest factor**5**which can be obtained using 7s only) - Display the calculated number of
**7’s**. - Append trailing zeros to the number made above.

- Count the number of

**Corner Cases To be Considered:**

- If the count of 0s the array is 0(then, the task is to check if the count of 7s in the array is divisible by 50 or not.
- If the count of 7s is less than 5 and no 0 is present in the array, simply print “Not Possible”.
- If the count of 7s is less than 5 and 0 is present, simply print ‘0‘.

Below is the implementation of the above approach:

## C++

`// C++ Program for the above approach` `#include <bits/stdc++.h>` `using` `namespace` `std;` `// Print the largest number divisibe by 50` `void` `printLargestDivisible(` `int` `arr[], ` `int` `N)` `{` ` ` `int` `i, count0 = 0, count7 = 0;` ` ` `for` `(i = 0; i < N; i++) {` ` ` `// Counting number of 0s and 7s` ` ` `if` `(arr[i] == 0)` ` ` `count0++;` ` ` `else` ` ` `count7++;` ` ` `}` ` ` `// If count of 7 is divisible by 50` ` ` `if` `(count7 % 50 == 0) {` ` ` `while` `(count7--)` ` ` `cout << 7;` ` ` `while` `(count0--)` ` ` `cout << 0;` ` ` `}` ` ` `// If count of 7 is less than 5` ` ` `else` `if` `(count7 < 5) {` ` ` `if` `(count0 == 0)` ` ` `cout << ` `"No"` `;` ` ` `else` ` ` `cout << ` `"0"` `;` ` ` `}` ` ` `// If count of 7 is not` ` ` `// divisible by 50` ` ` `else` `{` ` ` `// Count of groups of 5 in which` ` ` `// count of 7s can be grouped` ` ` `count7 = count7 - count7 % 5;` ` ` `while` `(count7--)` ` ` `cout << 7;` ` ` `while` `(count0--)` ` ` `cout << 0;` ` ` `}` `}` `// Driver Code` `int` `main()` `{` ` ` `// Given array` ` ` `int` `arr[] = { 0, 7, 0, 7, 7, 7, 7, 0,` ` ` `0, 0, 0, 0, 0, 7, 7, 7 };` ` ` `// Size of the array` ` ` `int` `N = ` `sizeof` `(arr) / ` `sizeof` `(arr[0]);` ` ` `printLargestDivisible(arr, N);` ` ` `return` `0;` `}` |

## Java

`// Java program of the above approach` `import` `java.io.*;` `class` `GFG {` ` ` `// Print the largest number divisibe by 50` ` ` `static` `void` `printLargestDivisible(` `int` `arr[], ` `int` `N)` ` ` `{` ` ` `int` `i, count0 = ` `0` `, count7 = ` `0` `;` ` ` `for` `(i = ` `0` `; i < N; i++) {` ` ` `// Counting number of 0s and 7s` ` ` `if` `(arr[i] == ` `0` `)` ` ` `count0++;` ` ` `else` ` ` `count7++;` ` ` `}` ` ` `// If count of 7 is divisible by 50` ` ` `if` `(count7 % ` `50` `== ` `0` `) {` ` ` `while` `(count7 != ` `0` `)` ` ` `{` ` ` `System.out.print(` `7` `);` ` ` `count7 -= ` `1` `;` ` ` `}` ` ` `while` `(count0 != ` `0` `)` ` ` `{` ` ` `System.out.print(` `0` `);` ` ` `count0 -= ` `1` `;` ` ` `}` ` ` `}` ` ` `// If count of 7 is less than 5` ` ` `else` `if` `(count7 < ` `5` `) {` ` ` `if` `(count0 == ` `0` `)` ` ` `System.out.print(` `"No"` `);` ` ` `else` ` ` `System.out.print( ` `"0"` `);` ` ` `}` ` ` `// If count of 7 is not` ` ` `// divisible by 50` ` ` `else` `{` ` ` `// Count of groups of 5 in which` ` ` `// count of 7s can be grouped` ` ` `count7 = count7 - count7 % ` `5` `;` ` ` `while` `(count7 != ` `0` `)` ` ` `{` ` ` `System.out.print(` `7` `);` ` ` `count7 -= ` `1` `;` ` ` `}` ` ` `while` `(count0 != ` `0` `)` ` ` `{` ` ` `System.out.print(` `0` `);` ` ` `count0 -= ` `1` `;` ` ` `}` ` ` `}` ` ` `}` ` ` `// Driver Code` ` ` `public` `static` `void` `main(String[] args)` ` ` `{` ` ` `// Given array` ` ` `int` `arr[] = { ` `0` `, ` `7` `, ` `0` `, ` `7` `, ` `7` `, ` `7` `, ` `7` `, ` `0` `,` ` ` `0` `, ` `0` `, ` `0` `, ` `0` `, ` `0` `, ` `7` `, ` `7` `, ` `7` `};` ` ` `// Size of the array` ` ` `int` `N = arr.length;` ` ` `printLargestDivisible(arr, N);` ` ` `}` `}` `// This code is contributed by jana_sayantan.` |

## Python3

`# Python3 Program for the above approach` `# Print the largest number divisibe by 50` `def` `printLargestDivisible(arr, N) :` ` ` `count0 ` `=` `0` `; count7 ` `=` `0` `;` ` ` `for` `i ` `in` `range` `(N) :` ` ` `# Counting number of 0s and 7s` ` ` `if` `(arr[i] ` `=` `=` `0` `) :` ` ` `count0 ` `+` `=` `1` `;` ` ` `else` `:` ` ` `count7 ` `+` `=` `1` `;` ` ` `# If count of 7 is divisible by 50` ` ` `if` `(count7 ` `%` `50` `=` `=` `0` `) :` ` ` `while` `(count7) :` ` ` `count7 ` `-` `=` `1` `;` ` ` `print` `(` `7` `, end ` `=` `"");` ` ` ` ` `while` `(count0) :` ` ` `count0 ` `-` `=` `1` `;` ` ` `print` `(count0, end ` `=` `"");` ` ` `# If count of 7 is less than 5` ` ` `elif` `(count7 < ` `5` `) :` ` ` `if` `(count0 ` `=` `=` `0` `) :` ` ` `print` `(` `"No"` `, end ` `=` `"");` ` ` `else` `:` ` ` `print` `(` `"0"` `, end ` `=` `"");` ` ` `# If count of 7 is not` ` ` `# divisible by 50` ` ` `else` `:` ` ` `# Count of groups of 5 in which` ` ` `# count of 7s can be grouped` ` ` `count7 ` `=` `count7 ` `-` `count7 ` `%` `5` `;` ` ` ` ` `while` `(count7) :` ` ` `count7 ` `-` `=` `1` `;` ` ` `print` `(` `7` `, end ` `=` `"");` ` ` ` ` `while` `(count0) :` ` ` `count0 ` `-` `=` `1` `;` ` ` `print` `(` `0` `, end ` `=` `"");` `# Driver Code` `if` `__name__ ` `=` `=` `"__main__"` `:` ` ` `# Given array` ` ` `arr ` `=` `[ ` `0` `, ` `7` `, ` `0` `, ` `7` `, ` `7` `, ` `7` `, ` `7` `, ` `0` `, ` `0` `, ` `0` `, ` `0` `, ` `0` `, ` `0` `, ` `7` `, ` `7` `, ` `7` `];` ` ` `# Size of the array` ` ` `N ` `=` `len` `(arr);` ` ` `printLargestDivisible(arr, N);` ` ` `# This code is contributed by AnkThon` |

## C#

`// C# program of the above approach` `using` `System;` `public` `class` `GFG {` ` ` `// Print the largest number divisibe by 50` ` ` `static` `void` `printLargestDivisible(` `int` `[]arr, ` `int` `N)` ` ` `{` ` ` `int` `i, count0 = 0, count7 = 0;` ` ` `for` `(i = 0; i < N; i++)` ` ` `{` ` ` `// Counting number of 0s and 7s` ` ` `if` `(arr[i] == 0)` ` ` `count0++;` ` ` `else` ` ` `count7++;` ` ` `}` ` ` `// If count of 7 is divisible by 50` ` ` `if` `(count7 % 50 == 0) {` ` ` `while` `(count7 != 0)` ` ` `{` ` ` `Console.Write(7);` ` ` `count7 -= 1;` ` ` `}` ` ` `while` `(count0 != 0)` ` ` `{` ` ` `Console.Write(0);` ` ` `count0 -= 1;` ` ` `}` ` ` `}` ` ` `// If count of 7 is less than 5` ` ` `else` `if` `(count7 < 5) {` ` ` `if` `(count0 == 0)` ` ` `Console.Write(` `"No"` `);` ` ` `else` ` ` `Console.Write( ` `"0"` `);` ` ` `}` ` ` `// If count of 7 is not` ` ` `// divisible by 50` ` ` `else` `{` ` ` `// Count of groups of 5 in which` ` ` `// count of 7s can be grouped` ` ` `count7 = count7 - count7 % 5;` ` ` `while` `(count7 != 0)` ` ` `{` ` ` `Console.Write(7);` ` ` `count7 -= 1;` ` ` `}` ` ` `while` `(count0 != 0)` ` ` `{` ` ` `Console.Write(0);` ` ` `count0 -= 1;` ` ` `}` ` ` `}` ` ` `}` ` ` `// Driver Code` ` ` `public` `static` `void` `Main(String[] args)` ` ` `{` ` ` ` ` `// Given array` ` ` `int` `[]arr = { 0, 7, 0, 7, 7, 7, 7, 0,` ` ` `0, 0, 0, 0, 0, 7, 7, 7 };` ` ` `// Size of the array` ` ` `int` `N = arr.Length;` ` ` `printLargestDivisible(arr, N);` ` ` `}` `}` `// This code is contributed by shikhasingrajput` |

## Javascript

`<script>` `// Javascript Program for the above approach` `// Print the largest number divisibe by 50` `function` `printLargestDivisible(arr, N)` `{` ` ` `var` `i, count0 = 0, count7 = 0;` ` ` `for` `(i = 0; i < N; i++) {` ` ` `// Counting number of 0s and 7s` ` ` `if` `(arr[i] == 0)` ` ` `count0++;` ` ` `else` ` ` `count7++;` ` ` `}` ` ` `// If count of 7 is divisible by 50` ` ` `if` `(count7 % 50 == 0) {` ` ` `while` `(count7--)` ` ` `document.write(7);` ` ` `while` `(count0--)` ` ` `document.write(0);` ` ` `}` ` ` `// If count of 7 is less than 5` ` ` `else` `if` `(count7 < 5) {` ` ` `if` `(count0 == 0)` ` ` `document.write(` `"No"` `);` ` ` `else` ` ` `document.write(` `"0"` `);` ` ` `}` ` ` `// If count of 7 is not` ` ` `// divisible by 50` ` ` `else` `{` ` ` `// Count of groups of 5 in which` ` ` `// count of 7s can be grouped` ` ` `count7 = count7 - count7 % 5;` ` ` `while` `(count7--)` ` ` `document.write(7);` ` ` `while` `(count0--)` ` ` `document.write(0);` ` ` `}` `}` `// Driver Code` `// Given array` `var` `arr = [ 0, 7, 0, 7, 7, 7, 7, 0,` ` ` `0, 0, 0, 0, 0, 7, 7, 7 ];` `// Size of the array` `var` `N = arr.length;` `printLargestDivisible(arr, N);` `</script>` |

**Output:**

7777700000000

**Time Complexity: **O(N)

**Auxiliary Space:** O(1)

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