Given a set of candidate numbers (candidates) (without duplicates) and a target number (target), find all unique combinations in candidates where the candidate numbers sums to target.
The same repeated number may be chosen from candidates unlimited number of times.
Note:
All numbers (including target) will be positive integers.
The solution set must not contain duplicate combinations.
Example 1:
Input: candidates = [2,3,6,7], target = 7,
A solution set is:
[
[7],
[2,2,3]
]
Example 2:
Input: candidates = [2,3,5], target = 8,
A solution set is:
[
[2,2,2,2],
[2,3,3],
[3,5]
]
Solution:
class Solution {
public List<List<Integer>> combinationSum(int[] candidates, int target) {
List<List<Integer>> result = new ArrayList();
if (candidates == null || candidates.length == 0) return result;
backtrack(result, new ArrayList(), candidates, target, 0);
return result;
}
private void backtrack(List<List<Integer>> result, List<Integer> curr, int[] candidates, int target, int start) {
if (target < 0 || start >= candidates.length) {
return;
}
if (target == 0) {
result.add(new ArrayList(curr));
return;
}
backtrack(result, curr, candidates, target, start + 1);
curr.add(candidates[start]);
backtrack(result, curr, candidates, target - candidates[start], start);
curr.remove(curr.size() - 1);
}
}