#include "s0039_combination_sum.hpp"

void S0039::dfs(vector<int>& candidates, int target, vector<vector<int>>& ans,
                vector<int>& combine, int idx) {
  if (idx == candidates.size()) {
    return;
  }
  if (target == 0) {
    ans.emplace_back(combine);
    return;
  }
  // 直接跳过
  dfs(candidates, target, ans, combine, idx + 1);
  // 选择当前数
  if (target - candidates[idx] >= 0) {
    combine.emplace_back(candidates[idx]);
    dfs(candidates, target - candidates[idx], ans, combine, idx);
    combine.pop_back();
  }
}

vector<vector<int>> S0039::combinationSum(vector<int>& candidates, int target) {
  vector<vector<int>> ans;
  vector<int> combine;
  dfs(candidates, target, ans, combine, 0);
  return ans;
}