Given an array **arr[]** of **N** integers and an integer **X**, the task is to find the maximum possible sub-array sum after applying at most **X** swaps.

**Examples:**

Input:arr[] = {5, -1, 2, 3, 4, -2, 5}, X = 2

Output:19

Swap (arr[0], arr[1]) and (arr[5], arr[6]).

Now, the maximum sub-array sum will be (5 + 2 + 3 + 4 + 5) = 19

Input:arr[] = {-2, -3, -1, -10}, X = 10

Output:-1

**Approach:** For every possible sub-array, consider the elements which are not part of this sub-array as discarded. Now, while there are swaps left and the sum of the sub-array currently under consideration can be maximized i.e. the greatest element among the discarded elements can be swapped with the minimum element of the sub-array, keep updating the sum of the sub-array. When there are no swaps left or the sub-array sum cannot be further maximized, update the current maximum sub-array sum found so far which will be the required answer in the end.

Below is the implementation of the above approach:

`// C++ implementation of the approach ` `#include <bits/stdc++.h> ` `using` `namespace` `std; ` ` ` `// Function to return the maximum ` `// sub-array sum after at most x swaps ` `int` `SubarraySum(` `int` `a[], ` `int` `n, ` `int` `x) ` `{ ` ` ` `// To store the required answer ` ` ` `int` `ans = -10000; ` ` ` ` ` `// For all possible intervals ` ` ` `for` `(` `int` `i = 0; i < n; i++) { ` ` ` `for` `(` `int` `j = i; j < n; j++) { ` ` ` ` ` `// Keep current ans as zero ` ` ` `int` `curans = 0; ` ` ` ` ` `// To store the integers which are ` ` ` `// not part of the sub-array ` ` ` `// currently under consideration ` ` ` `priority_queue<` `int` `, vector<` `int` `> > pq; ` ` ` ` ` `// To store elements which are ` ` ` `// part of the sub-array ` ` ` `// currently under consideration ` ` ` `priority_queue<` `int` `, vector<` `int` `>, greater<` `int` `> > pq2; ` ` ` ` ` `// Create two sets ` ` ` `for` `(` `int` `k = 0; k < n; k++) { ` ` ` `if` `(k >= i && k <= j) { ` ` ` `curans += a[k]; ` ` ` `pq2.push(a[k]); ` ` ` `} ` ` ` `else` ` ` `pq.push(a[k]); ` ` ` `} ` ` ` `ans = max(ans, curans); ` ` ` ` ` `// Swap at most X elements ` ` ` `for` `(` `int` `k = 1; k <= x; k++) { ` ` ` `if` `(pq.empty() || pq2.empty() ` ` ` `|| pq2.top() >= pq.top()) ` ` ` `break` `; ` ` ` ` ` `// Remove the minimum of ` ` ` `// the taken elements ` ` ` `curans -= pq2.top(); ` ` ` `pq2.pop(); ` ` ` ` ` `// Add maximum of the ` ` ` `// discarded elements ` ` ` `curans += pq.top(); ` ` ` `pq.pop(); ` ` ` ` ` `// Update the answer ` ` ` `ans = max(ans, curans); ` ` ` `} ` ` ` `} ` ` ` `} ` ` ` ` ` `// Return the maximized sub-array sum ` ` ` `return` `ans; ` `} ` ` ` `// Driver code ` `int` `main() ` `{ ` ` ` `int` `a[] = { 5, -1, 2, 3, 4, -2, 5 }, x = 2; ` ` ` `int` `n = ` `sizeof` `(a) / ` `sizeof` `(a[0]); ` ` ` ` ` `cout << SubarraySum(a, n, x); ` ` ` ` ` `return` `0; ` `} ` |

*chevron_right*

*filter_none*

**Output:**

19

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the **DSA Self Paced Course** at a student-friendly price and become industry ready.

## Recommended Posts:

- Minimum swaps to reach permuted array with at most 2 positions left swaps allowed
- Minimum possible value T such that at most D Partitions of the Array having at most sum T is possible
- Lexicographically smallest array after at-most K consecutive swaps
- Largest permutation after at most k swaps
- Lexicographical smallest number after at most K consecutive swaps
- Maximum Subarray Sum after inverting at most two elements
- Maximum possible GCD after replacing at most one element in the given array
- Maximize the subarray sum after multiplying all elements of any subarray with X
- Largest lexicographic array with at-most K consecutive swaps
- Maximize distance between two elements of Array by at most X swaps
- Find lexicographically smallest string in at most one swaps
- Longest subarray of non-empty cells after removal of at most a single empty cell
- First subarray having sum at least half the maximum sum of any subarray of size K
- Maximum sum subarray removing at most one element
- Maximum subarray sum by flipping signs of at most K array elements
- Maximum Subset Sum possible by negating the entire sum after selecting the first Array element
- Find the longest common prefix between two strings after performing swaps on second string
- Maximum length of subarray such that sum of the subarray is even
- Maximum subarray sum in an array created after repeated concatenation
- Maximize the maximum subarray sum after removing atmost one element

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.