C++ 子集合枚举

给定一个正整数数组 nums[], 求所有可能的组合，使得组合中的元素和等于target, 例如: nums 为 {3, 4, 5},  target 为 9,  解为 {3, 3, 3}, {4, 5}

#include <algorithm>
#include <memory>
#include <string>
#include <vector>
#include <iostream>
#include <set>
#include <stack>
 
void backtrack(std::vector<int> &state, std::vector<int> &choices, int target, int total, int start, std::vector<std::vector<int>> &res)
{
 
  if (total == target)
  {
    res.push_back(state);
    return;
  }
 
  for (int i = start; i < choices.size(); i++)
  {
    int choice = choices[i];
 
    if (total + choice <= target)
    {
      total += choice;
      state.push_back(choice);
 
      backtrack(state, choices, target, total, i, res);
 
      total -= choice;
      state.pop_back();
    }
  }
}
 
int main()
{
  std::vector<int> choices = {3, 4, 5}; //set
  std::vector<int> state{}; //subset
  std::vector<std::vector<int>> res{}; //result
 
  int target = 9;
  int total = 0;
  int start = 0;
 
  backtrack(state, choices, target, total, start, res);
 
  for (auto vv : res)
  {
    for (auto v : vv)
    {
      std::cout << v << " ";
    }
    std::cout << "\n";
  }
 
  return 0;
}