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：
