《LeetCode力扣练习》代码随想录——回溯算法（组合总和—Java）

刷题思路来源于 代码随想录

39. 组合总和

• 回溯

  class Solution {
  
      private List<Integer> path = new ArrayList<>();
      private List<List<Integer>> result = new ArrayList<>();
  
      public List<List<Integer>> combinationSum(int[] candidates, int target) {
  
          Arrays.sort(candidates);
          backtrack(candidates, target, 0, 0);
          return result;
  
      }
  
      private void backtrack(int[] candidates, int target, int sum, int startIndex) {
  
          if (sum > target) {
              return;
          }
  
          if (sum == target) {
              result.add(new ArrayList<>(path));
              return;
          }
  
          for (int i = startIndex; i < candidates.length && sum + candidates[i] <= target; i++) {
  
              sum = sum + candidates[i];
              path.add(candidates[i]);
  
              backtrack(candidates, target, sum, i);
  
              sum = sum - candidates[i];
              path.remove(path.size() - 1);
  
          }
  
          return;
  
      }
  }