import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * 
		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.
		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 2,3,6,7 and target 7, 
		A solution set is: 
		[7] 
		[2, 2, 3] 
 *
 */

public class CombinationSum {	
	
//	168 / 168 test cases passed.
//	Status: Accepted
//	Runtime: 274 ms
//	Submitted: 7 minutes ago

	
	//時間複雜度O(n!) 空間複雜度O(n)
	public List<List<Integer>> sums = new ArrayList<List<Integer>>();
    public List<List<Integer>> combinationSum(int[] candidates, int target) {
    	Arrays.sort(candidates);
    	combinationSum(candidates, 0, new ArrayList<Integer>(), target);
    	return sums;
    }
    public void combinationSum(int[] candidates, Integer begin, List<Integer> sum, int target) {
    	if(target == 0) {
			sums.add(sum);
    		return;
    	}    	
		for (int i = begin; i < candidates.length && target >= candidates[i]; i++) {
			List<Integer> list = new ArrayList<Integer>(sum);
			list.add(candidates[i]);
			combinationSum(candidates, i, list, target - candidates[i]);
		}
    }
    
	public static void main(String[] args) {
//		System.out.println(combinationSum(new int[]{2, 3, 6, 7}, 7));
	}

}
 

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * 
		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 {
	
//	172 / 172 test cases passed.
//	Status: Accepted
//	Runtime: 270 ms
//	Submitted: 0 minutes ago
	
	//時間複雜度O(n!) 空間複雜度O(n)
	public List<List<Integer>> sums = new ArrayList<List<Integer>>();
	public List<List<Integer>> combinationSum2(int[] candidates, int target) {
		Arrays.sort(candidates);
		combinationSum2(candidates, 0, new ArrayList<Integer>(), target);
		return sums;
	}

	public void combinationSum2(int[] candidates, int begin, List<Integer> sum,
			int target) {
		if (target == 0) {
			sums.add(sum);
			return;
		}
		int pre = -1;
		for (int i = begin; i < candidates.length && candidates[i] <= target; i++) {
			//如果當前數和前一個數相同， 則此次迴圈直接跳過
			if(pre == candidates[i]) {
				continue;
			}
			List<Integer> list = new ArrayList<Integer>(sum);
			pre = candidates[i];
			list.add(candidates[i]);
			combinationSum2(candidates, i + 1, list, target - candidates[i]);
		}
	}
	public static void main(String[] args) {

	}

}