Return to Answer

std::string scale_Balancing(std::vector<int>& integerWeights, std::vector<int>& availableWeights) { int difference = std::abs(integerWeights[1] - integerWeights[0]); sort(availableWeights.begin(), availableWeights.end()); if (std::binary_search(availableWeights.begin(), availableWeights.end(), difference)) { return std::to_string(difference); } else if (auto sum_pair = find_pair_with_sum(availableWeights, difference)) { return std::to_string(sum_pair->first) + "," + std::to_string(sum_pair->second); } else if (auto diff_pair = find_pair_with_difference(availableWeights, difference)) { return std::to_string(sum_pair->first) + "," + std::to_string(sum_pair->second); } else {   return "NOT POSSIBLE"; } } 

std::string scale_Balancing(std::vector<int>& integerWeights, std::vector<int>& availableWeights) { int difference = std::abs(integerWeights[1] - integerWeights[0]); sort(availableWeights.begin(), availableWeights.end()); if (std::binary_search(availableWeights.begin(), availableWeights.end(), difference)) { return std::to_string(difference); }    auto sum_pair = find_pair_with_sum(availableWeights, difference); if (sum_pair) { return std::to_string(sum_pair->first) + "," + std::to_string(sum_pair->second); }    auto diff_pair = find_pair_with_difference(availableWeights, difference); if (diff_pair) { return std::to_string(sum_pair->first) + "," + std::to_string(sum_pair->second); }    return "NOT POSSIBLE"; } 

take the vectors as values, you probably want to pass the vectors as references to avoid making a copy.

for that purpose. If C++17 is not available then returning a std::pair<int, int> (with { -1, -1 } indicating “not found”) would be an alternative to a returning a vector.

Finally note that both functions can be implemented with \$ O(n) \$ complexity if the array is sorted, see for example

take the vectors as values, you probably want to pass them by reference to avoid making copies.

for that purpose. If C++17 is not available then returning a std::pair<int, int> (with { -1, -1 } indicating “not found”) would be an alternative to returning a vector.

Note that both functions can be implemented with \$ O(n) \$ complexity if the array is sorted, see for example

With those changes, the main function simplifies to

std::string scale_Balancing(std::vector<int>& integerWeights, std::vector<int>& availableWeights) { int difference = std::abs(integerWeights[1] - integerWeights[0]); sort(availableWeights.begin(), availableWeights.end()); if (std::binary_search(availableWeights.begin(), availableWeights.end(), difference)) { return std::to_string(difference); } else if (auto sum_pair = find_pair_with_sum(availableWeights, difference)) { return std::to_string(sum_pair->first) + "," + std::to_string(sum_pair->second); } else if (auto diff_pair = find_pair_with_difference(availableWeights, difference)) { return std::to_string(sum_pair->first) + "," + std::to_string(sum_pair->second); } else { return "NOT POSSIBLE"; } } 

Unnecessary includes: These

#include <algorithm> #include <functional> #include <numeric> 

are apparently not needed.

In your function

template <typename T> bool all_Positive(const T start, const T end) { T it; for (it = start; it != end; it++) { if (*it < 0) return false; } return true; } 

the test should be

 if (*it <= 0) return false; 

otherwise zero would qualify as positive number. As @tinstaafl already said, verifying the input is usually not necessary for programming challenges.

The functions

std::string find_2_Nums_That_Minus_To_Difference(std::vector<int> availableWeights, int difference) std::string scale_Balancing(std::vector<int> integerWeights, std::vector<int> availableWeights) 

take the vectors as values, you probably want to pass the vectors as references to avoid making a copy.

In scale_Balancing() a possible pair of weights adding to the difference is determined (and possibly discarded) before searching for a single weight.

It is also confusing that

std::vector<int> find_2_Nums_That_Add_To_Difference(...) 

returns a vector, but

std::string find_2_Nums_That_Minus_To_Difference(...) 

returns a string.

Both functions actually return a pair of integers or “nothing.” In C++17 you can use a

std::optional<std::pair<int, int>> 

for that purpose. If C++17 is not available then returning a std::pair<int, int> (with { -1, -1 } indicating “not found”) would be an alternative to a returning a vector.

Better (and slightly shorter) function names would be

find_pair_with_sum(std::vector<int>&nums, int sum) find_pair_with_difference(std::vector<int>&nums, int difference) 

Finally note that both functions can be implemented with \$ O(n) \$ complexity, see for example

• Find a pair with the given difference
• Given an array A[] and a number x, check for pair in A[] with sum as x

Unnecessary includes: These

#include <algorithm> #include <functional> #include <numeric> 

are apparently not needed.

In your function

template <typename T> bool all_Positive(const T start, const T end) { T it; for (it = start; it != end; it++) { if (*it < 0) return false; } return true; } 

the test should be

 if (*it <= 0) return false; 

otherwise zero would qualify as positive number. As @tinstaafl already said, verifying the input is usually not necessary for programming challenges.

The functions

std::string find_2_Nums_That_Minus_To_Difference(std::vector<int> availableWeights, int difference) std::string scale_Balancing(std::vector<int> integerWeights, std::vector<int> availableWeights) 

take the vectors as values, you probably want to pass the vectors as references to avoid making a copy.

In scale_Balancing() a possible pair of weights adding to the difference is determined (and possibly discarded) before searching for a single weight.

It is also confusing that

std::vector<int> find_2_Nums_That_Add_To_Difference(...) 

returns a vector, but

std::string find_2_Nums_That_Minus_To_Difference(...) 

returns a string.

Both functions actually return a pair of integers or “nothing.” In C++17 you can use a

std::optional<std::pair<int, int>> 

for that purpose. If C++17 is not available then returning a std::pair<int, int> (with { -1, -1 } indicating “not found”) would be an alternative to a returning a vector.

Better (and slightly shorter) function names would be

find_pair_with_sum(std::vector<int>&nums, int sum) find_pair_with_difference(std::vector<int>&nums, int difference) 

Finally note that both functions can be implemented with \$ O(n) \$ complexity if the array is sorted, see for example

• Find a pair with the given difference
• Given an array A[] and a number x, check for pair in A[] with sum as x