C++ Function Lambda

#include <functional>
#include <iostream>

int main() {
  int a = 5, b = -5;

  auto lmbd = [&](int a) -> void {
    --a;
    --b;
  };

  std::function<void(int)> func = [&](int a) -> void {
    --a;
    --b;
  };

  func(a);

  std::cout << a << ' ' << b << std::endl;

  return 0;
}

class Solution {
public:
  bool canPartitionKSubsets(vector<int> &nums, int k) {
    const int n = nums.size();

    size_t sum = 0;
    for (auto num : nums) {
      sum += num;
    }
    if (sum % k != 0) {
      return false;
    }

    const int t = sum / k;
    bool flag = false;
     
    function<void(int, int)> func = [&](int mask, int cur) -> void {
      if (flag || cur > t) {
        return;
      } else if (cur == t) {
        --k;
        cur = 0;
        if (k == 0) {
          flag = true;
          return;
        }
      }

      for (int i = 0; i < nums.size(); ++i) {
        if ((mask & (1 << i)) == 0) {
          func(mask | (1 << i), cur + nums[i]);
        }
      }
    };

    func(0, 0);

    return flag;
  }
};