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Combination Sum.java
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Combination Sum.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]
]
time = O(2^n * n)
space = O(n)
*/
class Solution {
public List<List<Integer>> combinationSum(int[] candidates, int target) {
List<List<Integer>> result = new ArrayList<>();
if (candidates == null) {
return result;
}
Arrays.sort(candidates);
dfs(result, new ArrayList<>(), 0, target, candidates);
return result;
}
private void dfs(List<List<Integer>> result, List<Integer> list, int start, int remain, int[] candidates) {
if (remain < 0) {
return;
}
if (remain == 0) {
result.add(new ArrayList<>(list));
return;
}
for (int i = start; i < candidates.length; i++) {
list.add(candidates[i]);
dfs(result, list, i, remain - candidates[i], candidates);
list.remove(list.size() - 1);
}
}
}