216 accepted

Author: aQua

Algorithms/0216.combination-sum-iii/README.md

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+# [216. Combination Sum III](https://leetcode.com/problems/combination-sum-iii/)
+
+## 题目
+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.
+
+ Example 1:
+```
+Input:  k = 3,  n = 7
+Output: [[1,2,4]]
+```
+ Example 2:
+```
+Input:  k = 3,  n = 9
+Output: [[1,2,6], [1,3,5], [2,3,4]]
+```
+
+
+Credits:Special thanks to @mithmatt for adding this problem and creating all test cases.
+
+## 解题思路
+
+见程序注释

Algorithms/0216.combination-sum-iii/combination-sum-iii.go

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+package Problem0216
+
+func combinationSum3(k int, n int) [][]int {
+	res := [][]int{}
+	temp := make([]int, k+1)
+	used := make([]bool, 10)
+
+	var dfs func(int, int)
+	dfs = func(idx, remain int) {
+		if idx == k {
+			if remain < 10 && !used[remain] {
+				temp[idx] = remain
+				t := make([]int, k)
+				copy(t, temp[1:])
+				res = append(res, t)
+			}
+			return
+		}
+
+		for i := temp[idx-1] + 1; i < 10; i++ {
+			if remain-i  < i {
+				return
+			}
+			used[i] = true
+			temp[idx] = i
+			dfs(idx+1, remain-i)
+			used[i] = false
+		}
+	}
+
+	dfs(1, n)
+
+	return res
+}

Algorithms/0216.combination-sum-iii/combination-sum-iii_test.go

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+package Problem0216
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type question struct {
+	para
+	ans
+}
+
+// para 是参数
+type para struct {
+	k int
+	n int
+}
+
+// ans 是答案
+type ans struct {
+	one [][]int
+}
+
+func Test_Problem0216(t *testing.T) {
+	ast := assert.New(t)
+
+	qs := []question{
+
+		question{
+			para{
+				9,
+				45,
+			},
+			ans{[][]int{
+				[]int{1, 2, 3, 4, 5, 6, 7, 8, 9},
+			}},
+		},
+
+		question{
+			para{
+				3,
+				7,
+			},
+			ans{[][]int{
+				[]int{1, 2, 4},
+			}},
+		},
+
+		question{
+			para{
+				3,
+				9,
+			},
+			ans{[][]int{
+				[]int{1, 2, 6},
+				[]int{1, 3, 5},
+				[]int{2, 3, 4},
+			}},
+		},
+
+		// 如需多个测试，可以复制上方元素。
+	}
+
+	for _, q := range qs {
+		a, p := q.ans, q.para
+		fmt.Printf("~~%v~~\n", p)
+
+		ast.Equal(a.one, combinationSum3(p.k, p.n), "输入:%v", p)
+	}
+}