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73 lines
1.5 KiB
Markdown
Executable File
73 lines
1.5 KiB
Markdown
Executable File
# [216. Combination Sum III](https://leetcode.com/problems/combination-sum-iii/)
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## 题目
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Find all possible combinations of **k** numbers that add up to a number **n**, given that only numbers from 1 to 9 can be used and each combination should be a unique set of numbers.
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**Note**:
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- All numbers will be positive integers.
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- The solution set must not contain duplicate combinations.
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**Example 1**:
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Input: k = 3, n = 7
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Output: [[1,2,4]]
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**Example 2**:
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Input: k = 3, n = 9
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Output: [[1,2,6], [1,3,5], [2,3,4]]
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## 题目大意
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找出所有相加之和为 n 的 k 个数的组合。组合中只允许含有 1 - 9 的正整数，并且每种组合中不存在重复的数字。
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说明：
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- 所有数字都是正整数。
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- 解集不能包含重复的组合。
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## 解题思路
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- 这一题比第 39 题还要简单一些，在第 39 题上稍加改动就可以解出这一道题。
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- 第 39 题是给出数组，这一道题数组是固定死的 [1,2,3,4,5,6,7,8,9]，并且数字不能重复使用。
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## 代码
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```go
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package leetcode
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func combinationSum3(k int, n int) [][]int {
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if k == 0 {
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return [][]int{}
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}
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c, res := []int{}, [][]int{}
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findcombinationSum3(k, n, 1, c, &res)
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return res
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}
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func findcombinationSum3(k, target, index int, c []int, res *[][]int) {
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if target == 0 {
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if len(c) == k {
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b := make([]int, len(c))
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copy(b, c)
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*res = append(*res, b)
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}
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return
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}
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for i := index; i < 10; i++ {
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if target >= i {
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c = append(c, i)
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findcombinationSum3(k, target-i, i+1, c, res)
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c = c[:len(c)-1]
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}
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}
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}
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``` |