array: 组合

Change-Id: Id29ee259bc9223e2c73dfb2d18dde79dbe089cfa

Author: qieguo2016

go/leetcode/40.组合总和-ii.go

@@ -0,0 +1,80 @@
+/*
+ * @lc app=leetcode.cn id=40 lang=golang
+ *
+ * [40] 组合总和 II
+ *
+ * https://leetcode-cn.com/problems/combination-sum-ii/description/
+ *
+ * algorithms
+ * Medium (55.85%)
+ * Likes:    109
+ * Dislikes: 0
+ * Total Accepted:    15.1K
+ * Total Submissions: 27K
+ * Testcase Example:  '[10,1,2,7,6,1,5]\n8'
+ *
+ * 给定一个数组 candidates 和一个目标数 target ，找出 candidates 中所有可以使数字和为 target 的组合。
+ * 
+ * candidates 中的每个数字在每个组合中只能使用一次。
+ * 
+ * 说明：
+ * 
+ * 
+ * 所有数字（包括目标数）都是正整数。
+ * 解集不能包含重复的组合。 
+ * 
+ * 
+ * 示例 1:
+ * 
+ * 输入: candidates = [10,1,2,7,6,1,5], target = 8,
+ * 所求解集为:
+ * [
+ * ⁠ [1, 7],
+ * ⁠ [1, 2, 5],
+ * ⁠ [2, 6],
+ * ⁠ [1, 1, 6]
+ * ]
+ * 
+ * 
+ * 示例 2:
+ * 
+ * 输入: candidates = [2,5,2,1,2], target = 5,
+ * 所求解集为:
+ * [
+ * [1,2,2],
+ * [5]
+ * ]
+ * 
+ */
+
+import (
+	"sort"
+)
+
+func helper(arr []int, target int, start int, out *[]int, res *[][]int) {
+	if target < 0 {
+		return
+	}
+	if target == 0 {
+		*res = append(*res, append([]int{}, (*out)...))  // 复制值
+		return 
+	}
+	for i := start; i < len(arr); i++ {
+		if i > start && arr[i] == arr[i-1] {
+			continue
+		}
+		*out = append(*out, arr[i])
+		helper(arr, target-arr[i], i+1, out, res)
+		*out = (*out)[:len(*out)-1]
+	}
+}
+
+
+func combinationSum2(candidates []int, target int) [][]int {
+  out := []int{}
+	res := [][]int{}
+	sort.Ints(candidates)
+	helper(candidates, target, 0, &out, &res)
+	return res
+}
+