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| class Solution {
public List<List<Integer>> combinationSum3(int k, int n) {
List<List<Integer>> res = new ArrayList<>();
backtrack(res, new ArrayList<>(), n, k, 1);
return res;
}
public void backtrack(List<List<Integer>> res, List<Integer> path, int pathSum, int k, int start) {
if (path.size() == k && pathSum == 0) {
res.add(new ArrayList<>(path));
return;
} else if (path.size() == k || pathSum < 0) {
return;
}
for (int i = start; i <= 9; i++) {
path.add(i);
backtrack(res, path, pathSum - i, k, i + 1);
path.remove(path.size() - 1);
}
}
}
|