From 6b8b526dbfd646b46a997d4c001c248e11b2c10f Mon Sep 17 00:00:00 2001 From: qiufeihong2018 <15058301288@163.com> Date: Thu, 11 Apr 2024 17:20:55 +0800 Subject: [PATCH 01/12] =?UTF-8?q?refactor:=20=E4=BC=98=E5=8C=96=200209.?= =?UTF-8?q?=E9=95=BF=E5=BA=A6=E6=9C=80=E5=B0=8F=E7=9A=84=E5=AD=90=E6=95=B0?= =?UTF-8?q?=E7=BB=84.md=20=E7=9A=84=20Typescript=20=E5=86=99=E6=B3=95?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0209.长度最小的子数组.md | 29 +++++++++++------------ 1 file changed, 14 insertions(+), 15 deletions(-) diff --git a/problems/0209.长度最小的子数组.md b/problems/0209.长度最小的子数组.md index 5934d5e3..d2dfe1ee 100644 --- a/problems/0209.长度最小的子数组.md +++ b/problems/0209.长度最小的子数组.md @@ -270,22 +270,21 @@ var minSubArrayLen = function(target, nums) { ```typescript function minSubArrayLen(target: number, nums: number[]): number { - let left: number = 0, right: number = 0; - let res: number = nums.length + 1; - let sum: number = 0; - while (right < nums.length) { - sum += nums[right]; - if (sum >= target) { - // 不断移动左指针，直到不能再缩小为止 - while (sum - nums[left] >= target) { - sum -= nums[left++]; - } - res = Math.min(res, right - left + 1); - } - right++; + let left: number = 0, + res: number = Infinity, + subLen: number = 0, + sum: number = 0; + for (let right: number = 0; right < nums.length; right++) { + sum += nums[right]; + while (sum >= target) { + subLen = right - left + 1; + res = Math.min(res, subLen); + sum -= nums[left]; + left++; } - return res === nums.length + 1 ? 0 : res; -}; + } + return res === Infinity ? 0 : res; +} ``` ### Swift: From ff75974e30459b23a44d18a9180e8c9def80de46 Mon Sep 17 00:00:00 2001 From: qiufeihong2018 <15058301288@163.com> Date: Fri, 12 Apr 2024 16:33:29 +0800 Subject: [PATCH 02/12] =?UTF-8?q?fix:=20update=20=E6=95=B0=E7=BB=84?= =?UTF-8?q?=E6=80=BB=E7=BB=93=E7=AF=87=E5=92=8C=E6=95=B0=E7=BB=84=E7=90=86?= =?UTF-8?q?=E8=AE=BA=E5=9F=BA=E7=A1=80?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/数组总结篇.md | 2 +- problems/数组理论基础.md | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/problems/数组总结篇.md b/problems/数组总结篇.md index 7550ce02..d6a4e540 100644 --- a/problems/数组总结篇.md +++ b/problems/数组总结篇.md @@ -16,7 +16,7 @@ **数组是存放在连续内存空间上的相同类型数据的集合。** -数组可以方便的通过下标索引的方式获取到下标下对应的数据。 +数组可以方便的通过下标索引的方式获取到下标对应的数据。 举一个字符数组的例子，如图所示： diff --git a/problems/数组理论基础.md b/problems/数组理论基础.md index d104c883..1eb5b3f5 100644 --- a/problems/数组理论基础.md +++ b/problems/数组理论基础.md @@ -16,7 +16,7 @@ **数组是存放在连续内存空间上的相同类型数据的集合。** -数组可以方便的通过下标索引的方式获取到下标下对应的数据。 +数组可以方便的通过下标索引的方式获取到下标对应的数据。 举一个字符数组的例子，如图所示： From 3c9d6c408ac7286f19ddc096623b4454b3e8765c Mon Sep 17 00:00:00 2001 From: qiufeihong2018 <15058301288@163.com> Date: Fri, 12 Apr 2024 16:40:11 +0800 Subject: [PATCH 03/12] =?UTF-8?q?fix:=20update=20=E6=95=B0=E7=BB=84?= =?UTF-8?q?=E6=80=BB=E7=BB=93=E7=AF=87=E5=92=8C=E6=95=B0=E7=BB=84=E7=90=86?= =?UTF-8?q?=E8=AE=BA=E5=9F=BA=E7=A1=80?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/数组总结篇.md | 2 +- problems/数组理论基础.md | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/problems/数组总结篇.md b/problems/数组总结篇.md index d6a4e540..64658036 100644 --- a/problems/数组总结篇.md +++ b/problems/数组总结篇.md @@ -27,7 +27,7 @@ * **数组下标都是从0开始的。** * **数组内存空间的地址是连续的** -正是**因为数组的在内存空间的地址是连续的，所以我们在删除或者增添元素的时候，就难免要移动其他元素的地址。** +正是**因为数组在内存空间的地址是连续的，所以我们在删除或者增添元素的时候，就难免要移动其他元素的地址。** 例如删除下标为3的元素，需要对下标为3的元素后面的所有元素都要做移动操作，如图所示： diff --git a/problems/数组理论基础.md b/problems/数组理论基础.md index 1eb5b3f5..3492f4cc 100644 --- a/problems/数组理论基础.md +++ b/problems/数组理论基础.md @@ -29,7 +29,7 @@ * **数组下标都是从0开始的。** * **数组内存空间的地址是连续的** -正是**因为数组的在内存空间的地址是连续的，所以我们在删除或者增添元素的时候，就难免要移动其他元素的地址。** +正是**因为数组在内存空间的地址是连续的，所以我们在删除或者增添元素的时候，就难免要移动其他元素的地址。** 例如删除下标为3的元素，需要对下标为3的元素后面的所有元素都要做移动操作，如图所示： From 1f94655e9a3f2a91075b43477ef2cbe648891083 Mon Sep 17 00:00:00 2001 From: qiufeihong2018 <15058301288@163.com> Date: Tue, 23 Apr 2024 15:26:56 +0800 Subject: [PATCH 04/12] =?UTF-8?q?refactor:=20=E4=BC=98=E5=8C=960019.?= =?UTF-8?q?=E5=88=A0=E9=99=A4=E9=93=BE=E8=A1=A8=E7=9A=84=E5=80=92=E6=95=B0?= =?UTF-8?q?=E7=AC=ACN=E4=B8=AA=E8=8A=82=E7=82=B9.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- ...0019.删除链表的倒数第N个节点.md | 24 +++++++++++-------- 1 file changed, 14 insertions(+), 10 deletions(-) diff --git a/problems/0019.删除链表的倒数第N个节点.md b/problems/0019.删除链表的倒数第N个节点.md index 9e180f75..4a973edb 100644 --- a/problems/0019.删除链表的倒数第N个节点.md +++ b/problems/0019.删除链表的倒数第N个节点.md @@ -22,10 +22,12 @@ 输入：head = [1,2,3,4,5], n = 2 输出：[1,2,3,5] + 示例 2： 输入：head = [1], n = 1 输出：[] + 示例 3： 输入：head = [1,2], n = 1 @@ -193,16 +195,18 @@ func removeNthFromEnd(head *ListNode, n int) *ListNode { * @param {number} n * @return {ListNode} */ -var removeNthFromEnd = function(head, n) { - let ret = new ListNode(0, head), - slow = fast = ret; - while(n--) fast = fast.next; - while (fast.next !== null) { - fast = fast.next; - slow = slow.next - }; - slow.next = slow.next.next; - return ret.next; +var removeNthFromEnd = function (head, n) { + // 创建哨兵节点，简化解题逻辑 + let dummyHead = new ListNode(0, head); + let fast = dummyHead; + let slow = dummyHead; + while (n--) fast = fast.next; + while (fast.next !== null) { + slow = slow.next; + fast = fast.next; + } + slow.next = slow.next.next; + return dummyHead.next; }; ``` ### TypeScript: From f755ecc5fcce894cdbcc9c7eadfaf7bb123a3b1b Mon Sep 17 00:00:00 2001 From: qiufeihong2018 <15058301288@163.com> Date: Thu, 25 Apr 2024 17:34:06 +0800 Subject: [PATCH 05/12] =?UTF-8?q?refactor:=20=E4=BC=98=E5=8C=96=E4=BA=8C?= =?UTF-8?q?=E5=8F=89=E6=A0=91=E7=9A=84=E9=80=92=E5=BD=92=E9=81=8D=E5=8E=86?= =?UTF-8?q?.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/二叉树的递归遍历.md | 111 ++++++++++++++++++--------- 1 file changed, 75 insertions(+), 36 deletions(-) diff --git a/problems/二叉树的递归遍历.md b/problems/二叉树的递归遍历.md index 4621d4a7..ac42f69f 100644 --- a/problems/二叉树的递归遍历.md +++ b/problems/二叉树的递归遍历.md @@ -48,7 +48,7 @@ void traversal(TreeNode* cur, vector& vec) if (cur == NULL) return; ``` -3. **确定单层递归的逻辑**：前序遍历是中左右的循序，所以在单层递归的逻辑，是要先取中节点的数值，代码如下： +3. **确定单层递归的逻辑**：前序遍历是中左右的顺序，所以在单层递归的逻辑，是要先取中节点的数值，代码如下： ```cpp vec.push_back(cur->val); // 中 @@ -287,52 +287,91 @@ func postorderTraversal(root *TreeNode) (res []int) { 前序遍历： ```Javascript var preorderTraversal = function(root) { - let res=[]; - const dfs=function(root){ - if(root===null)return ; - //先序遍历所以从父节点开始 - res.push(root.val); - //递归左子树 - dfs(root.left); - //递归右子树 - dfs(root.right); - } - //只使用一个参数 使用闭包进行存储结果 - dfs(root); - return res; +// 第一种 +// let res=[]; +// const dfs=function(root){ +// if(root===null)return ; +// //先序遍历所以从父节点开始 +// res.push(root.val); +// //递归左子树 +// dfs(root.left); +// //递归右子树 +// dfs(root.right); +// } +// //只使用一个参数 使用闭包进行存储结果 +// dfs(root); +// return res; +// 第二种 + return root + ? [ + // 前序遍历：中左右 + root.val, + // 递归左子树 + ...preorderTraversal(root.left), + // 递归右子树 + ...preorderTraversal(root.right), + ] + : []; }; ``` 中序遍历 ```javascript var inorderTraversal = function(root) { - let res=[]; - const dfs=function(root){ - if(root===null){ - return ; - } - dfs(root.left); - res.push(root.val); - dfs(root.right); - } - dfs(root); - return res; +// 第一种 + + // let res=[]; + // const dfs=function(root){ + // if(root===null){ + // return ; + // } + // dfs(root.left); + // res.push(root.val); + // dfs(root.right); + // } + // dfs(root); + // return res; + +// 第二种 + return root + ? [ + // 中序遍历：左中右 + // 递归左子树 + ...inorderTraversal(root.left), + root.val, + // 递归右子树 + ...inorderTraversal(root.right), + ] + : []; }; ``` 后序遍历 ```javascript var postorderTraversal = function(root) { - let res=[]; - const dfs=function(root){ - if(root===null){ - return ; - } - dfs(root.left); - dfs(root.right); - res.push(root.val); - } - dfs(root); - return res; + // 第一种 + // let res=[]; + // const dfs=function(root){ + // if(root===null){ + // return ; + // } + // dfs(root.left); + // dfs(root.right); + // res.push(root.val); + // } + // dfs(root); + // return res; + + // 第二种 + // 后续遍历：左右中 + return root + ? [ + // 递归左子树 + ...postorderTraversal(root.left), + // 递归右子树 + ...postorderTraversal(root.right), + root.val, + ] + : []; }; ``` From 5ee2f42edb5765f6e28f2022fbcd257f27914b06 Mon Sep 17 00:00:00 2001 From: qiufeihong2018 <15058301288@163.com> Date: Mon, 29 Apr 2024 16:12:38 +0800 Subject: [PATCH 06/12] =?UTF-8?q?refactor:=200102.=E4=BA=8C=E5=8F=89?= =?UTF-8?q?=E6=A0=91=E7=9A=84=E5=B1=82=E5=BA=8F=E9=81=8D=E5=8E=86.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0102.二叉树的层序遍历.md | 40 ++++++++++++----------- problems/图论深搜理论基础.md | 2 +- 2 files changed, 22 insertions(+), 20 deletions(-) diff --git a/problems/0102.二叉树的层序遍历.md b/problems/0102.二叉树的层序遍历.md index 4411b560..d834eef7 100644 --- a/problems/0102.二叉树的层序遍历.md +++ b/problems/0102.二叉树的层序遍历.md @@ -692,27 +692,29 @@ func levelOrderBottom(root *TreeNode) [][]int { #### Javascript: ```javascript -var levelOrderBottom = function(root) { - let res = [], queue = []; - queue.push(root); - while(queue.length && root!==null) { - // 存放当前层级节点数组 - let curLevel = []; - // 计算当前层级节点数量 - let length = queue.length; - while(length--) { - let node = queue.shift(); - // 把当前层节点存入curLevel数组 - curLevel.push(node.val); - // 把下一层级的左右节点存入queue队列 - node.left && queue.push(node.left); - node.right && queue.push(node.right); - } - // 从数组前头插入值，避免最后反转数组，减少运算时间 - res.unshift(curLevel); +var levelOrderBottom = function (root) { + let res = [], + queue = []; + queue.push(root); + while (queue.length && root !== null) { + // 存放当前层级节点数组 + let curLevel = []; + // 计算当前层级节点数量 + let length = queue.length; + while (length--) { + let node = queue.shift(); + // 把当前层节点存入curLevel数组 + curLevel.push(node.val); + // 把下一层级的左右节点存入queue队列 + node.left && queue.push(node.left); + node.right && queue.push(node.right); } - return res; + // 从数组前头插入值，避免最后反转数组，减少运算时间 + res.unshift(curLevel); + } + return res; }; + ``` #### TypeScript: diff --git a/problems/图论深搜理论基础.md b/problems/图论深搜理论基础.md index 7f847f8f..15c5af3a 100644 --- a/problems/图论深搜理论基础.md +++ b/problems/图论深搜理论基础.md @@ -71,7 +71,7 @@ 有递归的地方就有回溯，那么回溯在哪里呢？ -就地递归函数的下面，例如如下代码： +就递归函数的下面，例如如下代码： ```cpp void dfs(参数) { From d7863c9dbfb124c93a1e4d589827b8397448553c Mon Sep 17 00:00:00 2001 From: qiufeihong2018 <15058301288@163.com> Date: Mon, 29 Apr 2024 16:36:42 +0800 Subject: [PATCH 07/12] =?UTF-8?q?refactor:=200102.=E4=BA=8C=E5=8F=89?= =?UTF-8?q?=E6=A0=91=E7=9A=84=E5=B1=82=E5=BA=8F=E9=81=8D=E5=8E=86.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0102.二叉树的层序遍历.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/problems/0102.二叉树的层序遍历.md b/problems/0102.二叉树的层序遍历.md index d834eef7..b9943f39 100644 --- a/problems/0102.二叉树的层序遍历.md +++ b/problems/0102.二叉树的层序遍历.md @@ -1142,7 +1142,7 @@ impl Solution { ### 思路 -本题就是层序遍历的时候把一层求个总和在取一个均值。 +本题就是层序遍历的时候把一层求个总和再取一个均值。 C++代码: From 4ca945f998d047eb7a0d9ea9308e53f46fd274fa Mon Sep 17 00:00:00 2001 From: qiufeihong2018 <15058301288@163.com> Date: Mon, 29 Apr 2024 17:08:26 +0800 Subject: [PATCH 08/12] =?UTF-8?q?refactor:=200102.=E4=BA=8C=E5=8F=89?= =?UTF-8?q?=E6=A0=91=E7=9A=84=E5=B1=82=E5=BA=8F=E9=81=8D=E5=8E=86.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0102.二叉树的层序遍历.md | 78 ++++++++++++----------- 1 file changed, 40 insertions(+), 38 deletions(-) diff --git a/problems/0102.二叉树的层序遍历.md b/problems/0102.二叉树的层序遍历.md index b9943f39..0a98ab88 100644 --- a/problems/0102.二叉树的层序遍历.md +++ b/problems/0102.二叉树的层序遍历.md @@ -1297,26 +1297,26 @@ func averageOfLevels(root *TreeNode) []float64 { ```javascript var averageOfLevels = function(root) { - //层级平均值 - let res = [], queue = []; - queue.push(root); - - while(queue.length && root!==null) { - //每一层节点个数 - let length = queue.length; - //sum记录每一层的和 - let sum = 0; - for(let i=0; i < length; i++) { - let node = queue.shift(); - sum += node.val; - node.left && queue.push(node.left); - node.right && queue.push(node.right); - } - //每一层的平均值存入数组res - res.push(sum/length); + let res = [], + queue = []; + queue.push(root); + while (queue.length) { + // 每一层节点个数; + let lengthLevel = queue.length, + len = queue.length, + // sum记录每一层的和; + sum = 0; + while (lengthLevel--) { + const node = queue.shift(); + sum += node.val; + // 队列存放下一层节点 + node.left && queue.push(node.left); + node.right && queue.push(node.right); } - - return res; + // 求平均值 + res.push(sum / len); + } + return res; }; ``` @@ -1927,26 +1927,28 @@ func max(x, y int) int { #### Javascript： ```javascript -var largestValues = function(root) { - //使用层序遍历 - let res = [], queue = []; - queue.push(root); - - while(root !== null && queue.length) { - //设置max初始值就是队列的第一个元素 - let max = queue[0].val; - let length = queue.length; - while(length--) { - let node = queue.shift(); - max = max > node.val ? max : node.val; - node.left && queue.push(node.left); - node.right && queue.push(node.right); - } - //把每一层的最大值放到res数组 - res.push(max); - } - +var largestValues = function (root) { + let res = [], + queue = []; + queue.push(root); + if (root === null) { return res; + } + while (queue.length) { + let lengthLevel = queue.length, + // 初始值设为负无穷大 + max = -Infinity; + while (lengthLevel--) { + const node = queue.shift(); + // 在当前层中找到最大值 + max = Math.max(max, node.val); + // 找到下一层的节点 + node.left && queue.push(node.left); + node.right && queue.push(node.right); + } + res.push(max); + } + return res; }; ``` From 2d37cd39e02789d09387b5dc1176fd8f71adf769 Mon Sep 17 00:00:00 2001 From: qiufeihong2018 <15058301288@163.com> Date: Mon, 29 Apr 2024 18:19:48 +0800 Subject: [PATCH 09/12] =?UTF-8?q?refactor:=200102.=E4=BA=8C=E5=8F=89?= =?UTF-8?q?=E6=A0=91=E7=9A=84=E5=B1=82=E5=BA=8F=E9=81=8D=E5=8E=86?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0102.二叉树的层序遍历.md | 30 ++++++++++++----------- 1 file changed, 16 insertions(+), 14 deletions(-) diff --git a/problems/0102.二叉树的层序遍历.md b/problems/0102.二叉树的层序遍历.md index 0a98ab88..1cb916b4 100644 --- a/problems/0102.二叉树的层序遍历.md +++ b/problems/0102.二叉树的层序遍历.md @@ -2809,21 +2809,23 @@ func maxDepth(root *TreeNode) int { * @param {TreeNode} root * @return {number} */ -var maxDepth = function(root) { - // 最大的深度就是二叉树的层数 - if (root === null) return 0; - let queue = [root]; - let height = 0; - while (queue.length) { - let n = queue.length; - height++; - for (let i=0; i Date: Wed, 1 May 2024 16:08:36 +0800 Subject: [PATCH 10/12] =?UTF-8?q?refactor:=200077.=E7=BB=84=E5=90=88.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0077.组合.md | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/problems/0077.组合.md b/problems/0077.组合.md index 103fb627..35ed5fad 100644 --- a/problems/0077.组合.md +++ b/problems/0077.组合.md @@ -469,6 +469,32 @@ func dfs(n int, k int, start int) { ``` ### Javascript +未剪枝： + +```js +var combine = function (n, k) { + // 回溯法 + let result = [], + path = []; + let backtracking = (_n, _k, startIndex) => { + // 终止条件 + if (path.length === _k) { + result.push(path.slice()); + return; + } + // 循环本层集合元素 + for (let i = startIndex; i <= _n; i++) { + path.push(i); + // 递归 + backtracking(_n, _k, i + 1); + // 回溯操作 + path.pop(); + } + }; + backtracking(n, k, 1); + return result; +}; +``` 剪枝： From d1d7cdeecd2922b86edccb7cfd135117a5926a60 Mon Sep 17 00:00:00 2001 From: qiufeihong2018 <15058301288@163.com> Date: Wed, 1 May 2024 19:10:32 +0800 Subject: [PATCH 11/12] =?UTF-8?q?refactor:=200077.=E7=BB=84=E5=90=88.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0077.组合.md | 38 +++++++++++++++++++++----------------- 1 file changed, 21 insertions(+), 17 deletions(-) diff --git a/problems/0077.组合.md b/problems/0077.组合.md index 35ed5fad..f394b3d8 100644 --- a/problems/0077.组合.md +++ b/problems/0077.组合.md @@ -499,24 +499,28 @@ var combine = function (n, k) { 剪枝： ```javascript -let result = [] -let path = [] -var combine = function(n, k) { - result = [] - combineHelper(n, k, 1) - return result +var combine = function (n, k) { + // 回溯法 + let result = [], + path = []; + let backtracking = (_n, _k, startIndex) => { + // 终止条件 + if (path.length === _k) { + result.push(path.slice()); + return; + } + // 循环本层集合元素 + for (let i = startIndex; i <= _n - (_k - path.length) + 1; i++) { + path.push(i); + // 递归 + backtracking(_n, _k, i + 1); + // 回溯操作 + path.pop(); + } + }; + backtracking(n, k, 1); + return result; }; -const combineHelper = (n, k, startIndex) => { - if (path.length === k) { - result.push([...path]) - return - } - for (let i = startIndex; i <= n - (k - path.length) + 1; ++i) { - path.push(i) - combineHelper(n, k, i + 1) - path.pop() - } -} ``` ### TypeScript From 5e6a657d90fe9a3ba7c86aa8505898e0f7ed739b Mon Sep 17 00:00:00 2001 From: qiufeihong2018 <15058301288@163.com> Date: Wed, 1 May 2024 19:51:01 +0800 Subject: [PATCH 12/12] =?UTF-8?q?refactor:=200216.=E7=BB=84=E5=90=88?= =?UTF-8?q?=E6=80=BB=E5=92=8CIII.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0216.组合总和III.md | 93 +++++++++++++++++++++++--------- 1 file changed, 68 insertions(+), 25 deletions(-) diff --git a/problems/0216.组合总和III.md b/problems/0216.组合总和III.md index ac28f9fc..d331726e 100644 --- a/problems/0216.组合总和III.md +++ b/problems/0216.组合总和III.md @@ -417,6 +417,7 @@ func dfs(k, n int, start int, sum int) { ``` ### JavaScript +- 未剪枝： ```js /** @@ -424,32 +425,74 @@ func dfs(k, n int, start int, sum int) { * @param {number} n * @return {number[][]} */ -var combinationSum3 = function(k, n) { - let res = []; - let path = []; - let sum = 0; - const dfs = (path,index) => { - // 剪枝操作 - if (sum > n){ - return - } - if (path.length == k) { - if(sum == n){ - res.push([...path]); - return - } - } - for (let i = index; i <= 9 - (k-path.length) + 1;i++) { - path.push(i); - sum = sum + i; - index += 1; - dfs(path,index); - sum -= i - path.pop() - } +var combinationSum3 = function (k, n) { + // 回溯法 + let result = [], + path = []; + const backtracking = (_k, targetSum, sum, startIndex) => { + // 终止条件 + if (path.length === _k) { + if (sum === targetSum) { + result.push(path.slice()); + } + // 如果总和不相等，就直接返回 + return; } - dfs(path,1); - return res + + // 循环当前节点，因为只使用数字1到9，所以最大是9 + for (let i = startIndex; i <= 9; i++) { + path.push(i); + sum += i; + // 回调函数 + backtracking(_k, targetSum, sum, i + 1); + // 回溯 + sum -= i; + path.pop(); + } + }; + backtracking(k, n, 0, 1); + return result; +}; +``` + +- 剪枝： + +```js +/** + * @param {number} k + * @param {number} n + * @return {number[][]} + */ +var combinationSum3 = function (k, n) { + // 回溯法 + let result = [], + path = []; + const backtracking = (_k, targetSum, sum, startIndex) => { + if (sum > targetSum) { + return; + } + // 终止条件 + if (path.length === _k) { + if (sum === targetSum) { + result.push(path.slice()); + } + // 如果总和不相等，就直接返回 + return; + } + + // 循环当前节点，因为只使用数字1到9，所以最大是9 + for (let i = startIndex; i <= 9 - (_k - path.length) + 1; i++) { + path.push(i); + sum += i; + // 回调函数 + backtracking(_k, targetSum, sum, i + 1); + // 回溯 + sum -= i; + path.pop(); + } + }; + backtracking(k, n, 0, 1); + return result; }; ```