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| class Solution {
public List<List<Integer>> combine(int n, int k) {
List<List<Integer>> resultList = new ArrayList<>();
List<Integer> numList = new ArrayList<>();
dfs(resultList, numList, n, 1, k);
return resultList;
}
private void dfs(List<List<Integer>> resultList, List<Integer> numList, int n, int i, int k) {
if (numList.size() == k) {
resultList.add(new ArrayList<>(numList));
return;
}
if (n - i + 1 < k - numList.size()) {
return;
}
numList.add(i);
dfs(resultList, numList, n, i + 1, k);
numList.remove(numList.size() - 1);
dfs(resultList, numList, n, i + 1, k);
}
}
|