# Maximize the sum of X+Y elements by picking X and Y elements from 1st and 2nd array

Given two arrays of size N, and two numbers X and Y, the task is to maximize the sum by considering the below points:

- Pick
**x**values from the first array and**y**values from the second array such that the sum of X+Y values is maximum. - It is given that X + Y is equal to N.

**Examples:**

Input:arr1[] = {1, 4, 1}, arr2[] = {2, 5, 3}, N = 3, X = 2, Y = 1

Output:8

In order to maximize sum from 2 arrays,

pick 1st and 2nd element from first array and 3rd from second array.

Input:A[] = {1, 4, 1, 2}, B[] = {4, 3, 2, 5}, N = 4, X = 2, Y = 2

Output:14

**Approach: **A greedy approach can be used to solve the above problem. Below are the required steps:

- Find those elements of arrays first that have maximum value by finding the highest difference between elements of two arrays.
- For that, find the absolute difference between the value of the first and second array and then store it in some another array.
- Sort this array in decreasing order.
- While sorting, track the original positions of elements in the arrays.
- Now compare the elements of the two arrays and add the greater value to the maxAmount.
- If both have the same value, add an element of the first array if X is not zero else add an element of the second array.
- After traversing the arrays completely return the maxAmount calculated.

Below is the implementation of above approach :

`// C++ program to print the maximum ` `// possible sum from two arrays. ` `#include <bits/stdc++.h> ` `using` `namespace` `std; ` ` ` `// class that store values of two arrays ` `// and also store their absolute difference ` `class` `triplet { ` `public` `: ` ` ` `int` `first; ` ` ` `int` `second; ` ` ` `int` `diff; ` ` ` `triplet(` `int` `f, ` `int` `s, ` `int` `d) ` ` ` `: first(f), second(s), diff(d) ` ` ` `{ ` ` ` `} ` `}; ` ` ` `// Compare function used to sort array in decreasing order ` `bool` `compare(triplet& a, triplet& b) ` `{ ` ` ` `return` `a.diff > b.diff; ` `// decreasing order ` `} ` ` ` `/// Function to find the maximum possible ` `/// sum that can be generated from 2 arrays ` `int` `findMaxAmount(` `int` `arr1[], ` `int` `arr2[], ` `int` `n, ` `int` `x, ` `int` `y) ` `{ ` ` ` `// vector where each index stores 3 things: ` ` ` `// Value of 1st array ` ` ` `// Value of 2nd array ` ` ` `// Their absolute difference ` ` ` `vector<triplet> v; ` ` ` ` ` `for` `(` `int` `i = 0; i < n; i++) { ` ` ` `triplet t(arr1[i], arr2[i], ` `abs` `(arr1[i] - arr2[i])); ` ` ` `v.push_back(t); ` ` ` `} ` ` ` ` ` `// sort according to their absolute difference ` ` ` `sort(v.begin(), v.end(), compare); ` ` ` ` ` `// it will store maximum sum ` ` ` `int` `maxAmount = 0; ` ` ` ` ` `int` `i = 0; ` ` ` ` ` `// Run loop for N times or ` ` ` `// value of X or Y becomes zero ` ` ` `while` `(i < n && x > 0 && y > 0) { ` ` ` ` ` `// if 1st array element has greater ` ` ` `// value, add it to maxAmount ` ` ` `if` `(v[i].first > v[i].second) { ` ` ` `maxAmount += v[i].first; ` ` ` `x--; ` ` ` `} ` ` ` ` ` `// if 2nd array element has greater ` ` ` `// value, add it to maxAmount ` ` ` `if` `(v[i].first < v[i].second) { ` ` ` `maxAmount += v[i].second; ` ` ` `y--; ` ` ` `} ` ` ` ` ` `// if both have same value, add element ` ` ` `// of first array if X is not zero ` ` ` `// else add element of second array ` ` ` `if` `(v[i].first == v[i].second) { ` ` ` `if` `(x > 0) { ` ` ` `maxAmount += v[i].first; ` ` ` `x--; ` ` ` `} ` ` ` `else` `if` `(y > 0) { ` ` ` `maxAmount += v[i].second; ` ` ` `y--; ` ` ` `} ` ` ` `} ` ` ` ` ` `// increment after picking element ` ` ` `i++; ` ` ` `} ` ` ` ` ` `// add the remaining values ` ` ` `// of first array to maxAmount ` ` ` `while` `(i < v.size() && x--) { ` ` ` `maxAmount += v[i++].first; ` ` ` `} ` ` ` ` ` `// add the remaining values of ` ` ` `// second array to maxAmount ` ` ` `while` `(i < v.size() && y--) { ` ` ` `maxAmount += v[i++].second; ` ` ` `} ` ` ` ` ` `return` `maxAmount; ` `} ` ` ` `// Driver Code ` `int` `main() ` `{ ` ` ` `int` `A[] = { 1, 4, 1, 2 }; ` ` ` `int` `B[] = { 4, 3, 2, 5 }; ` ` ` `int` `n = ` `sizeof` `(A) / ` `sizeof` `(A[0]); ` ` ` ` ` `int` `X = 2, Y = 2; ` ` ` ` ` `cout << findMaxAmount(A, B, n, X, Y) << ` `"\n"` `; ` `} ` |

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**Output:**

14

**Time complexity:** O(N log N)

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