> For the complete documentation index, see [llms.txt](https://gl01.gitbook.io/gfg-editorials/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://gl01.gitbook.io/gfg-editorials/2024/03-2024-march-2/03-largest-number-formed-from-an-array.md).

# 03. Largest Number formed from an Array

The problem can be found at the following link: [Question Link](https://www.geeksforgeeks.org/problems/largest-number-formed-from-an-array1117/1)

## My Approach

* I Defined a custom comparison function func that compares two strings a and b based on their concatenation in different orders (a + b vs. b + a).
* The goal is to arrange the strings in a way that concatenating them results in the largest possible number.
* Use the sort function to sort the array of strings (arr) in descending order based on the custom comparison function func.
* This step ensures that the strings are arranged to form the largest number when concatenated.
* Concatenate the sorted strings to form the final result.
* Return the concatenated string as the output.

## Time and Auxiliary Space Complexity

* **Time Complexity**: `O(NlogN)`, where N is the number of strings in the array.
* **Auxiliary Space Complexity**: `O(N)`, where N is the number of strings in the array.

## Code (C++)

```cpp
bool func(string& a, string& b)
{
    return a+b > b+a;
}
class Solution{
public:
	string printLargest(int n, vector<string> &arr)
	{
	    sort(arr.begin(), arr.end(), func);
        string out;
        for (auto s : arr)
            out+=s;
        return out;
	}
};
```

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