LeetCode | Combination Sum II

題目

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

Each number in C may only be used once in the combination.

Note:

• All numbers (including target) will be positive integers.
• Elements in a combination (a₁, a₂, … , a_k) must be in non-descending order. (ie, a₁ ≤ a₂ ≤ … ≤ a_k).
• The solution set must not contain duplicate combinations.

  For example, given candidate set 10,1,2,7,6,1,5 and target 8,
  A solution set is:
  [1, 7]
[1, 2, 5]
[2, 6]
[1, 1, 6]

  分析

  和Combination Sum思路完全一致，注意去重即可。

  代碼

  import java.util.ArrayList;
  import java.util.Arrays;
  
  public class CombinationSumII {
  	public ArrayList> combinationSum2(int[] num, int target) {
  		Arrays.sort(num);
  		ArrayList> results = new ArrayList>();
  		ArrayList list = new ArrayList();
  		solve(results, list, num, 0, target);
  		return results;
  	}
  
  	private void solve(ArrayList> results,
  			ArrayList list, int[] num, int i, int target) {
  		if (target < 0) {
  			return;
  		}
  		if (target == 0) {
  			results.add(new ArrayList(list));
  			return;
  		}
  		for (int j = i; j < num.length && num[j] <= target; ++j) {
  			list.add(num[j]);
  			solve(results, list, num, j + 1, target - num[j]);
  			list.remove(list.size() - 1);
  			while (j < num.length - 1 && num[j] == num[j + 1]) {
  				++j;
  			}
  		}
  	}
  }