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CombinationSum39.java
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CombinationSum39.java
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/**
* 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]
* ]
*/
public class CombinationSum39 {
public List<List<Integer>> combinationSum(int[] candidates, int target) {
List<List<Integer>> res = new ArrayList<>();
helper(candidates, target, 0, new ArrayList<Integer>(), res);
return res;
}
private void helper(int[] candidates, int target, int start, List<Integer> path, List<List<Integer>> res) {
if (target < 0) return;
if (target == 0) {
List<Integer> newPath = new ArrayList<Integer>();
for (Integer i: path) newPath.add(i);
res.add(newPath);
}
for (int i = start; i<candidates.length; i++) {
int c = candidates[i];
int count = target / c;
if (count >= 1) {
for (int j=1; j<= count; j++) {path.add(c);}
while (count >= 1) {
helper(candidates, target - c * count, i+1, path, res);
path.remove(path.size() - 1);
count--;
}
}
}
}
}