Combination Sum II (Java)

LeetCode

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, … , ak) must be in non-descending order. (ie, a1 ≤ a2 ≤ … ≤ ak).
• 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] 

Solution: DFS

     Apply DFS continually check every combination, if any one meet the target put it into result arraylist.

	/*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, … , ak) must be in non-descending order. (ie, a1 ≤ a2 ≤ … ≤ ak).
	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]
	*/
	public class CombinationSumII {
	public ArrayList<ArrayList<Integer>> combinationSum2(int[] num, int target) {
	ArrayList<ArrayList<Integer>> result=new ArrayList<ArrayList<Integer>>();
	if (num==null||num.length==0){
	return result;
	}
	ArrayList<Integer> current=new ArrayList<Integer>();
	int start=0;
	Arrays.sort(num);
	buildResult(num,start, target, current, result);
	return result;
	}
	private void buildResult(int[] num, int start, int target, ArrayList<Integer> current, ArrayList<ArrayList<Integer>> result){
	if (target==0){
	ArrayList<Integer> temp=new ArrayList<Integer>(current);
	result.add(temp);
	return;
	}
	for (int i=start; i<num.length; i++){
	if (num[i]>target){
	continue;
	}
	current.add(num[i]);
	buildResult(num,i+1, target-num[i], current,result);
	current.remove(current.size()-1);
	while(i+1<num.length && num[i]==num[i+1]){
	i++;
	}
	}
	}
	}

view raw CombinationSumII.java hosted with ❤ by GitHub