Combination Sum

Description

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]
]

给出加数与和数，求出所有组合。

Solution

思路是与之前做过的查找解的题目相似： 把target减去候选数，得到剩余target，继续查找，直到target为0。

func combinationSum(candidates []int, target int) [][]int {
    sort.Ints(candidates)

    return doCombinationSum(candidates, target)
}

func doCombinationSum(candidates []int, target int) [][]int {
    res := [][]int{}

    if len(candidates) == 0 {
        return res
    }

    t := target - candidates[0]

    if t < 0 {
        return res
    } else if t == 0 {
        res = append(res, []int{candidates[0]})
    } else if t > 0 {
        res = doCombinationSum(candidates, t)
        for i, v := range res {
            res[i] = append([]int{candidates[0]}, v...)
        }
    }

    res = append(res, doCombinationSum(candidates[1:], target)...)

    return res
}

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