题目

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]
]
``````

Swift 题解

``````func combinationSum(_ candidates: [Int], _ target: Int) -> [[Int]] {
var result = [[Int]]()

var current = [Int]()

let sorted = candidates.sorted()

dfs(result: &result, current: &current, target: target, level: 0, candidates: sorted)

return result

}

func dfs(result: inout [[Int]], current: inout [Int], target: Int, level: Int, candidates: [Int]) {
if target == 0 {
result.append(current)
return
}

if target < 0 {
return
}

for i in level..<candidates.count {
current.append(candidates[i])
dfs(result: &result, current: &current, target: target - candidates[i], level: i, candidates: candidates)
current.removeLast()
}
}
``````