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39. Combination Sum

时间:2016-06-11 08:12:13      阅读:176      评论:0      收藏:0      [点我收藏+]

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Given a set of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.

The same repeated number may be chosen from C unlimited number of times.

Note:

  • All numbers (including target) will be positive integers.
  • The solution set must not contain duplicate combinations.

 

For example, given candidate set [2, 3, 6, 7] and target 7
A solution set is: 

[
  [7],
  [2, 2, 3]
]
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 Array Backtracking
 

 

class Solution {
  public List<List<Integer>> combinationSum(int[] candidates, int target) {
    Arrays.sort(candidates);

    ArrayList<List<Integer>> ret = new ArrayList<List<Integer>>();
    combinationSum(candidates, 0, target, new LinkedList<Integer>(), ret);
    return ret;
  }

  private void combinationSum(int[] candidates, int from, int target,
                              LinkedList<Integer> current, ArrayList<List<Integer>> ret)
  {
    for(int i = from; i<candidates.length; ++i)
    {
      int c = candidates[i];
      if(c > target)
        return;
      if(c == target)
      {
        LinkedList<Integer> sol = new LinkedList<Integer>(current);
        sol.add(c);
        ret.add(sol);
        return;
      }

      current.addLast(c);
      combinationSum(candidates, i, target -c, current, ret);
      current.removeLast();

    }
  }
}

 

 

 

 

39. Combination Sum

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原文地址:http://www.cnblogs.com/neweracoding/p/5574660.html

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