【leetcode】40. (Medium) Combination Sum II

题目链接

提交代码：

class Solution {
	public List<List<Integer>> combinationSum(int[] candidates, int target) {
		List<List<Integer>> result = new ArrayList<List<Integer>>();
		if(candidates==null)	return result;
		mergeSort(candidates, 0, candidates.length - 1);
		findCombination(result,new ArrayList<Integer>(),candidates,target,0);
		
		return result;
	}

	public void findCombination(List<List<Integer>> result,
			List<Integer> list,int[] candidates,int target,int pos) {
	
		if(target<0)	return;
		
		else if(target==0) {
			result.add(new ArrayList<>(list));
			return;
		}
		else {
			for(int i=pos;i<candidates.length;i++) {
				if(candidates[i]>target)	break;
				if(i>pos&&candidates[i]==candidates[i-1]) continue;
				list.add(candidates[i]);
				findCombination(result,list,candidates,target-candidates[i],i);
				list.remove(list.size()-1);
			}
		}
	}

	public void mergeSort(int[] nums, int left, int right) {
		if (left >= right)
			return;

		int mid = (left + right) / 2;
		mergeSort(nums, left, mid);
		mergeSort(nums, mid + 1, right);
		merge(nums, left, right, mid);
	}

	public void merge(int nums[], int left, int right, int mid) {
		if (left >= right)
			return;

		int len = right - left + 1;
		int[] tmp = new int[len];
		int i = left, j = mid + 1, k = 0;

		while (i <= mid && j <= right) {
			tmp[k++] = nums[i] < nums[j] ? nums[i++] : nums[j++];
		}
		while (i <= mid)
			tmp[k++] = nums[i++];
		while (j <= right)
			tmp[k++] = nums[j++];
		for (k = 0; k < len; k++)
			nums[left++] = tmp[k];
	}

}

运行结果：