dfs: 组合

Change-Id: I313e44461de5977cbdfac717470bf5dc25531dff

Author: qieguo2016

go/leetcode/216.组合总和-iii.go

@@ -0,0 +1,62 @@
+/*
+ * @lc app=leetcode.cn id=216 lang=golang
+ *
+ * [216] 组合总和 III
+ *
+ * https://leetcode-cn.com/problems/combination-sum-iii/description/
+ *
+ * algorithms
+ * Medium (69.01%)
+ * Likes:    71
+ * Dislikes: 0
+ * Total Accepted:    10.2K
+ * Total Submissions: 14.8K
+ * Testcase Example:  '3\n7'
+ *
+ * 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。
+ * 
+ * 说明：
+ * 
+ * 
+ * 所有数字都是正整数。
+ * 解集不能包含重复的组合。 
+ * 
+ * 
+ * 示例 1:
+ * 
+ * 输入: k = 3, n = 7
+ * 输出: [[1,2,4]]
+ * 
+ * 
+ * 示例 2:
+ * 
+ * 输入: k = 3, n = 9
+ * 输出: [[1,2,6], [1,3,5], [2,3,4]]
+ * 
+ * 
+ */
+
+// @lc code=start
+func combinationSum3(k int, n int) [][]int {
+	out := []int{}
+	res := [][]int{}
+	dfs(k, n, 1, 10, &out, &res)
+	return res
+}
+
+func dfs(k int, n int, start int, end int, out *[]int, res *[][]int) {
+	if k == 0 && n == 0 {
+		*res = append(*res, append([]int{}, (*out)...))
+		return
+	}
+	if k < 0 || n < 0 {
+		return
+	}
+	for i := start; i < end; i++ {
+		*out = append(*out, i)
+		dfs(k-1, n-i, i+1, end, out, res)
+		*out = (*out)[:len(*out)-1]
+	}
+}
+// @lc code=end
+