# Sum of minimum element of all subarrays of a sorted array

Given a sorted array A of n integers. The task is to find the sum of minimum of all possible subarrays of A.

Examples:

Input: A = [ 1, 2, 4, 5]
Output: 23
Subsequences are , , , , [1, 2], [2, 4], [4, 5] [1, 2, 4], [2, 4, 5], [1, 2, 4, 5]
Minimums are 1, 2, 4, 5, 1, 2, 4, 1, 2, 1.
Sum is 23

Input: A = [1, 2, 3]
Output: 10

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: The Naive approach is to generate all possible subarrays, find their minimum and add them to result.

Efficient Approach: It is given that the array is sorted, so observe that minimum element occurs N times, the second minimum occurs N-1 times and so on… Let’s take an example:

arr[] = {1, 2, 3}
Subarrays are {1}, {2}, {3}, {1, 2}, {2, 3}, {1, 2, 3}
Minimum of each subarray: {1}, {2}, {3}, {1}, {2}, {1}.
where
1 occurs 3 times i.e. n times where n = 3.
2 occurs 2 times i.e. n-1 times where n = 3.
3 occurs 1 times i.e. n-2 times where n = 3.

So, traverse the array and add current element i.e. (arr[i]* n-i) to the sum.

Below is the implementation of the above approach:

## C++

 `// C++ implementation of the above approach ` `#include ` `using` `namespace` `std; ` ` `  `// Function to find the sum ` `// of minimum of all subarrays ` `int` `findMinSum(``int` `arr[], ``int` `n) ` `{ ` ` `  `    ``int` `sum = 0; ` `    ``for` `(``int` `i = 0; i < n; i++) ` `        ``sum += arr[i] * (n - i); ` ` `  `    ``return` `sum; ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``int` `arr[] = { 3, 5, 7, 8 }; ` `    ``int` `n = ``sizeof``(arr) / ``sizeof``(arr); ` ` `  `    ``cout << findMinSum(arr, n); ` ` `  `    ``return` `0; ` `} `

## Java

 `// Java implementation of the above approach  ` `class` `GfG  ` `{ ` ` `  `// Function to find the sum  ` `// of minimum of all subarrays  ` `static` `int` `findMinSum(``int` `arr[], ``int` `n)  ` `{  ` ` `  `    ``int` `sum = ``0``;  ` `    ``for` `(``int` `i = ``0``; i < n; i++)  ` `        ``sum += arr[i] * (n - i);  ` ` `  `    ``return` `sum;  ` `}  ` ` `  `// Driver code  ` `public` `static` `void` `main(String[] args)  ` `{  ` `    ``int` `arr[] = { ``3``, ``5``, ``7``, ``8` `};  ` `    ``int` `n = arr.length;  ` ` `  `    ``System.out.println(findMinSum(arr, n));  ` `} ` `}  ` ` `  `// This code is contributed by Prerna Saini `

## Python3

 `# Python3 implementation of the  ` `# above approach  ` ` `  `# Function to find the sum  ` `# of minimum of all subarrays  ` `def` `findMinSum(arr, n): ` `    ``sum` `=` `0` `    ``for` `i ``in` `range``(``0``, n):  ` `        ``sum` `+``=` `arr[i] ``*` `(n ``-` `i)  ` `    ``return` `sum` ` `  `# Driver code  ` `arr ``=` `[``3``, ``5``, ``7``, ``8` `]  ` `n ``=` `len``(arr) ` ` `  `print``(findMinSum(arr, n))  ` ` `  `# This code has been contributed  ` `# by 29AjayKumar `

## C#

 `// C# implementation of the above approach  ` `using` `System; ` ` `  `class` `GfG  ` `{  ` ` `  `// Function to find the sum  ` `// of minimum of all subarrays  ` `static` `int` `findMinSum(``int` `[]arr, ``int` `n)  ` `{  ` ` `  `    ``int` `sum = 0;  ` `    ``for` `(``int` `i = 0; i < n; i++)  ` `        ``sum += arr[i] * (n - i);  ` ` `  `    ``return` `sum;  ` `}  ` ` `  `// Driver code  ` `public` `static` `void` `Main(String []args)  ` `{  ` `    ``int` `[]arr = { 3, 5, 7, 8 };  ` `    ``int` `n = arr.Length;  ` ` `  `    ``Console.WriteLine(findMinSum(arr, n));  ` `}  ` `}  ` ` `  `// This code is contributed by Arnab Kundu `

## PHP

 ` `

Output:

```49
```

Note: To find the Sum of maximum element of all subarrays in a sorted array, just traverse the array in reverse order and apply the same formula for Sum.

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