规范格式

leetcode/0039.Combination-Sum/39. Combination Sum.go

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+package leetcode
+
+import "sort"
+
+func combinationSum(candidates []int, target int) [][]int {
+	if len(candidates) == 0 {
+		return [][]int{}
+	}
+	c, res := []int{}, [][]int{}
+	sort.Ints(candidates)
+	findcombinationSum(candidates, target, 0, c, &res)
+	return res
+}
+
+func findcombinationSum(nums []int, target, index int, c []int, res *[][]int) {
+	if target <= 0 {
+		if target == 0 {
+			b := make([]int, len(c))
+			copy(b, c)
+			*res = append(*res, b)
+		}
+		return
+	}
+	for i := index; i < len(nums); i++ {
+		c = append(c, nums[i])
+		findcombinationSum(nums, target-nums[i], i, c, res) // 注意这里迭代的时候 index 依旧不变，因为一个元素可以取多次
+		c = c[:len(c)-1]
+	}
+}

leetcode/0039.Combination-Sum/39. Combination Sum_test.go

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+package leetcode
+
+import (
+	"fmt"
+	"testing"
+)
+
+type question39 struct {
+	para39
+	ans39
+}
+
+// para 是参数
+// one 代表第一个参数
+type para39 struct {
+	n []int
+	k int
+}
+
+// ans 是答案
+// one 代表第一个答案
+type ans39 struct {
+	one [][]int
+}
+
+func Test_Problem39(t *testing.T) {
+
+	qs := []question39{
+
+		question39{
+			para39{[]int{2, 3, 6, 7}, 7},
+			ans39{[][]int{[]int{7}, []int{2, 2, 3}}},
+		},
+
+		question39{
+			para39{[]int{2, 3, 5}, 8},
+			ans39{[][]int{[]int{2, 2, 2, 2}, []int{2, 3, 3}, []int{3, 5}}},
+		},
+	}
+
+	fmt.Printf("------------------------Leetcode Problem 39------------------------\n")
+
+	for _, q := range qs {
+		_, p := q.ans39, q.para39
+		fmt.Printf("【input】:%v       【output】:%v\n", p, combinationSum(p.n, p.k))
+	}
+	fmt.Printf("\n\n\n")
+}

leetcode/0039.Combination-Sum/README.md

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+# [39. Combination Sum](https://leetcode.com/problems/combination-sum/)
+
+
+## 题目
+
+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]
+    ]
+
+
+## 题目大意
+
+给定一个无重复元素的数组 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 中的数字可以无限制重复被选取。
+
+
+## 解题思路
+
+- 题目要求出总和为 sum 的所有组合，组合需要去重。
+- 这一题和第 47 题类似，只不过元素可以反复使用。