From 06ebd5f204f8a7012c1e4518ce778fa06750d7e6 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E5=93=88=E5=93=88=E5=93=88?= <76643786+Projecthappy@users.noreply.github.com> Date: Thu, 23 Mar 2023 00:08:57 +0800 Subject: [PATCH 01/14] =?UTF-8?q?Update=200454.=E5=9B=9B=E6=95=B0=E7=9B=B8?= =?UTF-8?q?=E5=8A=A0II.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 原先是先判断map中是否有这个key，后面更新时再get(key)，经过测试，直接使用getOrDefault()方法效率会更高一些，没有当前key时返回0，值为0就是没有当前key --- problems/0454.四数相加II.md | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-) diff --git a/problems/0454.四数相加II.md b/problems/0454.四数相加II.md index c2a5710f..411b60e8 100644 --- a/problems/0454.四数相加II.md +++ b/problems/0454.四数相加II.md @@ -97,26 +97,25 @@ Java： ```Java class Solution { public int fourSumCount(int[] nums1, int[] nums2, int[] nums3, int[] nums4) { - Map map = new HashMap<>(); - int temp; int res = 0; + Map map = new HashMap(); //统计两个数组中的元素之和，同时统计出现的次数，放入map for (int i : nums1) { for (int j : nums2) { - temp = i + j; - if (map.containsKey(temp)) { - map.put(temp, map.get(temp) + 1); + int tmp = map.getOrDefault(i + j, 0); + if (tmp == 0) { + map.put(i + j, 1); } else { - map.put(temp, 1); + map.replace(i + j, tmp + 1); } } } //统计剩余的两个元素的和，在map中找是否存在相加为0的情况，同时记录次数 for (int i : nums3) { for (int j : nums4) { - temp = i + j; - if (map.containsKey(0 - temp)) { - res += map.get(0 - temp); + int tmp = map.getOrDefault(0 - i - j, 0); + if (tmp != 0) { + res += tmp; } } } From 584654ba7ef0a791391ffb7745a52c23cf0981c0 Mon Sep 17 00:00:00 2001 From: lynn <435962415@qq.com> Date: Thu, 23 Mar 2023 10:57:32 +0800 Subject: [PATCH 02/14] =?UTF-8?q?=E5=A2=9E=E5=8A=A0=E4=BA=860056.=E5=90=88?= =?UTF-8?q?=E5=B9=B6=E5=8C=BA=E9=97=B4=E7=9A=84=E8=A7=A3=E6=B3=95=E4=BA=8C?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0056.合并区间.md | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) diff --git a/problems/0056.合并区间.md b/problems/0056.合并区间.md index d467ab1a..0daf5f9b 100644 --- a/problems/0056.合并区间.md +++ b/problems/0056.合并区间.md @@ -174,6 +174,34 @@ func max(a, b int) int { return b } ``` +```go +// 版本2 +func merge(intervals [][]int) [][]int { + if len(intervals) == 1 { + return intervals + } + sort.Slice(intervals, func(i, j int) bool { + return intervals[i][0] < intervals[j][0] + }) + res := make([][]int, 0) + res = append(res, intervals[0]) + for i := 1; i < len(intervals); i++ { + if intervals[i][0] <= res[len(res)-1][1]{ + res[len(res)-1][1] = max56(res[len(res)-1][1],intervals[i][1]) + } else { + res = append(res, intervals[i]) + } + } + return res +} +func max56(a, b int) int { + if a > b { + return a + } + return b +} +``` + ### Javascript ```javascript From 4b65ece9ed30a88962782f1742d2d07d53783010 Mon Sep 17 00:00:00 2001 From: "Mr.D" Date: Sun, 26 Mar 2023 16:52:18 +0800 Subject: [PATCH 03/14] Add another Rust solution --- problems/0001.两数之和.md | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/problems/0001.两数之和.md b/problems/0001.两数之和.md index b3abb991..eea3ba7a 100644 --- a/problems/0001.两数之和.md +++ b/problems/0001.两数之和.md @@ -216,6 +216,26 @@ impl Solution { } } ``` +Rust + +``` +use std::collections::HashMap; + +impl Solution { + pub fn two_sum(nums: Vec, target: i32) -> Vec { + let mut hm: HashMap = HashMap::new(); + for i in 0..nums.len() { + let j = target - nums[i]; + if hm.contains_key(&j) { + return vec![*hm.get(&j).unwrap(), i as i32] + } else { + hm.insert(nums[i], i as i32); + } + } + vec![-1, -1] + } +} +``` Javascript From 334f4a27de2ecc00134c6cf287f658758f856e6f Mon Sep 17 00:00:00 2001 From: hoxiansen <1365171821@qq.com> Date: Tue, 28 Mar 2023 09:40:19 +0000 Subject: [PATCH 04/14] =?UTF-8?q?Update=200518.=E9=9B=B6=E9=92=B1=E5=85=91?= =?UTF-8?q?=E6=8D=A2II.md=20=E8=A1=A5=E5=85=85=E4=BA=8C=E7=BB=B4dp?= =?UTF-8?q?=E6=95=B0=E7=BB=84=E7=9A=84Java=E4=BB=A3=E7=A0=81?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0518.零钱兑换II.md | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/problems/0518.零钱兑换II.md b/problems/0518.零钱兑换II.md index 3fd03e16..eb5a844c 100644 --- a/problems/0518.零钱兑换II.md +++ b/problems/0518.零钱兑换II.md @@ -215,6 +215,27 @@ class Solution { } } ``` +```Java +// 二维dp数组版本，方便理解 +class Solution { + public int change(int amount, int[] coins) { + int[][] dp = new int[coins.length][amount + 1]; + // 只有一种硬币的情况 + for (int i = 0; i <= amount; i += coins[0]) { + dp[0][i] = 1; + } + for (int i = 1; i < coins.length; i++) { + for (int j = 0; j <= amount; j++) { + // 第i种硬币使用0~k次，求和 + for (int k = 0; k * coins[i] <= j; k++) { + dp[i][j] += dp[i - 1][j - k * coins[i]]; + } + } + } + return dp[coins.length - 1][amount]; + } +} +``` Python： From b18aba58bcfa66b31fb9d40ffb6805f75f5bd3ea Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E8=8A=B1=E6=97=A0=E7=BC=BA?= Date: Tue, 28 Mar 2023 22:22:14 +0800 Subject: [PATCH 05/14] =?UTF-8?q?=E6=9B=B4=E6=94=B9=E9=94=99=E5=88=AB?= =?UTF-8?q?=E5=AD=97?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 将爬楼梯文件中的中字更正为了种 --- problems/0070.爬楼梯.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/problems/0070.爬楼梯.md b/problems/0070.爬楼梯.md index d8246223..a06ee91e 100644 --- a/problems/0070.爬楼梯.md +++ b/problems/0070.爬楼梯.md @@ -72,7 +72,7 @@ dp[i]： 爬到第i层楼梯，有dp[i]种方法 3. dp数组如何初始化 -再回顾一下dp[i]的定义：爬到第i层楼梯，有dp[i]中方法。 +再回顾一下dp[i]的定义：爬到第i层楼梯，有dp[i]种方法。 那么i为0，dp[i]应该是多少呢，这个可以有很多解释，但基本都是直接奔着答案去解释的。 From f6a22863841064c9f5c61ad606fa10f293494de9 Mon Sep 17 00:00:00 2001 From: fw_qaq Date: Wed, 29 Mar 2023 11:52:19 +0800 Subject: [PATCH 06/14] =?UTF-8?q?Update=20=E6=A0=B9=E6=8D=AE=E8=BA=AB?= =?UTF-8?q?=E9=AB=98=E9=87=8D=E5=BB=BA=E9=98=9F=E5=88=97=EF=BC=88vector?= =?UTF-8?q?=E5=8E=9F=E7=90=86=E8=AE=B2=E8=A7=A3=EF=BC=89.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- ...高重建队列（vector原理讲解）.md | 29 +++++++++++++++++++ 1 file changed, 29 insertions(+) diff --git a/problems/根据身高重建队列（vector原理讲解）.md b/problems/根据身高重建队列（vector原理讲解）.md index 94d94e38..4f8cab82 100644 --- a/problems/根据身高重建队列（vector原理讲解）.md +++ b/problems/根据身高重建队列（vector原理讲解）.md @@ -177,6 +177,35 @@ Java： Python： +Rust： + +```rust +// 版本二，使用list（链表） +use std::collections::LinkedList; +impl Solution{ + pub fn reconstruct_queue(mut people: Vec>) -> Vec> { + let mut queue = LinkedList::new(); + people.sort_by(|a, b| { + if a[0] == b[0] { + return a[1].cmp(&b[1]); + } + b[0].cmp(&a[0]) + }); + queue.push_back(people[0].clone()); + for v in people.iter().skip(1) { + if queue.len() > v[1] as usize { + let mut back_link = queue.split_off(v[1] as usize); + queue.push_back(v.clone()); + queue.append(&mut back_link); + } else { + queue.push_back(v.clone()); + } + } + queue.into_iter().collect() + } +} +``` + Go： From 7e02650599bd98ef92f017f2838c09c17235a502 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E8=8A=B1=E6=97=A0=E7=BC=BA?= Date: Wed, 29 Mar 2023 20:21:27 +0800 Subject: [PATCH 07/14] =?UTF-8?q?update=20=E4=BD=BF=E7=94=A8=E6=9C=80?= =?UTF-8?q?=E5=B0=8F=E8=8A=B1=E8=B4=B9=E7=88=AC=E6=A5=BC=E6=A2=AF.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 优化文档中的语言描述 --- problems/0746.使用最小花费爬楼梯.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/problems/0746.使用最小花费爬楼梯.md b/problems/0746.使用最小花费爬楼梯.md index d6b3a177..d7258d45 100644 --- a/problems/0746.使用最小花费爬楼梯.md +++ b/problems/0746.使用最小花费爬楼梯.md @@ -92,7 +92,7 @@ dp[i - 2] 跳到 dp[i] 需要花费 dp[i - 2] + cost[i - 2]。 这里就要说明本题力扣为什么改题意，而且修改题意之后 就清晰很多的原因了。 -新题目描述中明确说了 “你可以选择从下标为 0 或下标为 1 的台阶开始爬楼梯。” 也就是说 从 到达 第 0 个台阶是不花费的，但从 第0 个台阶 往上跳的话，需要花费 cost[0]。 +新题目描述中明确说了 “你可以选择从下标为 0 或下标为 1 的台阶开始爬楼梯。” 也就是说 到达 第 0 个台阶是不花费的，但从 第0 个台阶 往上跳的话，需要花费 cost[0]。 所以初始化 dp[0] = 0，dp[1] = 0; From 02f9c26f696774c9db2aa7bef4ac25f9d4b28803 Mon Sep 17 00:00:00 2001 From: Yuhao Ju Date: Sat, 1 Apr 2023 12:42:01 +0800 Subject: [PATCH 08/14] =?UTF-8?q?updaye=200232.=E7=94=A8=E6=A0=88=E5=AE=9E?= =?UTF-8?q?=E7=8E=B0=E9=98=9F=E5=88=97=EF=BC=9A=E6=B7=BB=E5=8A=A0=E5=A4=8D?= =?UTF-8?q?=E6=9D=82=E5=BA=A6=E5=88=86=E6=9E=90?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0232.用栈实现队列.md | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/problems/0232.用栈实现队列.md b/problems/0232.用栈实现队列.md index efeb1046..4a57ee96 100644 --- a/problems/0232.用栈实现队列.md +++ b/problems/0232.用栈实现队列.md @@ -112,6 +112,10 @@ public: ``` +* 时间复杂度: push和empty为O(1), pop和peek为O(n) +* 空间复杂度: O(n) + + ## 拓展 可以看出peek()的实现，直接复用了pop()， 要不然，对stOut判空的逻辑又要重写一遍。 From 1b6e26be2bf4f2dd584b3b59e4781a9d79cd4b48 Mon Sep 17 00:00:00 2001 From: Yuhao Ju Date: Sat, 1 Apr 2023 12:45:02 +0800 Subject: [PATCH 09/14] =?UTF-8?q?update=200225.=E7=94=A8=E9=98=9F=E5=88=97?= =?UTF-8?q?=E5=AE=9E=E7=8E=B0=E6=A0=88=EF=BC=9A=E6=B7=BB=E5=8A=A0=E5=A4=8D?= =?UTF-8?q?=E6=9D=82=E5=BA=A6=E5=88=86=E6=9E=90?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0225.用队列实现栈.md | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/problems/0225.用队列实现栈.md b/problems/0225.用队列实现栈.md index 16b9e47c..bad2faec 100644 --- a/problems/0225.用队列实现栈.md +++ b/problems/0225.用队列实现栈.md @@ -111,6 +111,8 @@ public: } }; ``` +* 时间复杂度: push为O(n)，其他为O(1) +* 空间复杂度: O(n) # 优化 @@ -156,6 +158,9 @@ public: } }; ``` +* 时间复杂度: push为O(n)，其他为O(1) +* 空间复杂度: O(n) + # 其他语言版本 From 916718824bd6fe521ee2164b29f71d11633828a7 Mon Sep 17 00:00:00 2001 From: Yuhao Ju Date: Sat, 1 Apr 2023 12:47:36 +0800 Subject: [PATCH 10/14] =?UTF-8?q?update=200020.=E6=9C=89=E6=95=88=E7=9A=84?= =?UTF-8?q?=E6=8B=AC=E5=8F=B7=EF=BC=9A=E6=B7=BB=E5=8A=A0=E5=A4=8D=E6=9D=82?= =?UTF-8?q?=E5=BA=A6=E5=88=86=E6=9E=90?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0020.有效的括号.md | 3 +++ 1 file changed, 3 insertions(+) diff --git a/problems/0020.有效的括号.md b/problems/0020.有效的括号.md index a25129c5..213d61b7 100644 --- a/problems/0020.有效的括号.md +++ b/problems/0020.有效的括号.md @@ -135,6 +135,9 @@ public: }; ``` +* 时间复杂度: O(n) +* 空间复杂度: O(n) + 技巧性的东西没有固定的学习方法，还是要多看多练，自己灵活运用了。 From 2633b1a346e106e8d14ee6404f1cf50cfb83a0af Mon Sep 17 00:00:00 2001 From: Yuhao Ju Date: Sat, 1 Apr 2023 12:50:29 +0800 Subject: [PATCH 11/14] =?UTF-8?q?update=201047.=E5=88=A0=E9=99=A4=E5=AD=97?= =?UTF-8?q?=E7=AC=A6=E4=B8=B2=E4=B8=AD=E7=9A=84=E6=89=80=E6=9C=89=E7=9B=B8?= =?UTF-8?q?=E9=82=BB=E9=87=8D=E5=A4=8D=E9=A1=B9:=20=E6=B7=BB=E5=8A=A0?= =?UTF-8?q?=E5=A4=8D=E6=9D=82=E5=BA=A6=E5=88=86=E6=9E=90?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/1047.删除字符串中的所有相邻重复项.md | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/problems/1047.删除字符串中的所有相邻重复项.md b/problems/1047.删除字符串中的所有相邻重复项.md index 810f7292..694f1a92 100644 --- a/problems/1047.删除字符串中的所有相邻重复项.md +++ b/problems/1047.删除字符串中的所有相邻重复项.md @@ -77,6 +77,9 @@ public: } }; ``` +* 时间复杂度: O(n) +* 空间复杂度: O(n) + 当然可以拿字符串直接作为栈，这样省去了栈还要转为字符串的操作。 @@ -99,6 +102,8 @@ public: } }; ``` +* 时间复杂度: O(n) +* 空间复杂度: O(1)，返回值不计空间复杂度 ## 题外话 From 6cd25d1fc5f98a02c7ef1ad52ad416c39d7357a4 Mon Sep 17 00:00:00 2001 From: Yuhao Ju Date: Sat, 1 Apr 2023 12:53:40 +0800 Subject: [PATCH 12/14] =?UTF-8?q?update=200150.=E9=80=86=E6=B3=A2=E5=85=B0?= =?UTF-8?q?=E8=A1=A8=E8=BE=BE=E5=BC=8F=E6=B1=82=E5=80=BC:=20=E6=B7=BB?= =?UTF-8?q?=E5=8A=A0=E5=A4=8D=E6=9D=82=E5=BA=A6=E5=88=86=E6=9E=90?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0150.逆波兰表达式求值.md | 3 +++ 1 file changed, 3 insertions(+) diff --git a/problems/0150.逆波兰表达式求值.md b/problems/0150.逆波兰表达式求值.md index f0323bc4..09cc4f96 100644 --- a/problems/0150.逆波兰表达式求值.md +++ b/problems/0150.逆波兰表达式求值.md @@ -113,6 +113,9 @@ public: }; ``` +* 时间复杂度: O(n) +* 空间复杂度: O(n) + ## 题外话 From 1662ac347d28f35073066dba2761cd9d0c4bcf35 Mon Sep 17 00:00:00 2001 From: Yuhao Ju Date: Sat, 1 Apr 2023 12:55:37 +0800 Subject: [PATCH 13/14] =?UTF-8?q?update=200239.=E6=BB=91=E5=8A=A8=E7=AA=97?= =?UTF-8?q?=E5=8F=A3=E6=9C=80=E5=A4=A7=E5=80=BC=EF=BC=9A=E6=B7=BB=E5=8A=A0?= =?UTF-8?q?=E5=A4=8D=E6=9D=82=E5=BA=A6=E5=88=86=E6=9E=90?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0239.滑动窗口最大值.md | 3 +++ 1 file changed, 3 insertions(+) diff --git a/problems/0239.滑动窗口最大值.md b/problems/0239.滑动窗口最大值.md index 540ab5d7..f1c4b76c 100644 --- a/problems/0239.滑动窗口最大值.md +++ b/problems/0239.滑动窗口最大值.md @@ -184,6 +184,9 @@ public: } }; ``` +* 时间复杂度: O(n) +* 空间复杂度: O(k) + 再来看一下时间复杂度，使用单调队列的时间复杂度是 O(n)。 From b28ba70ee1464fbd915c5d655bd6865a7d2d66e0 Mon Sep 17 00:00:00 2001 From: Yuhao Ju Date: Sat, 1 Apr 2023 12:57:24 +0800 Subject: [PATCH 14/14] =?UTF-8?q?update=20=200347.=E5=89=8DK=E4=B8=AA?= =?UTF-8?q?=E9=AB=98=E9=A2=91=E5=85=83=E7=B4=A0=EF=BC=9A=E6=B7=BB=E5=8A=A0?= =?UTF-8?q?=E5=A4=8D=E6=9D=82=E5=BA=A6=E5=88=86=E6=9E=90?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0347.前K个高频元素.md | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/problems/0347.前K个高频元素.md b/problems/0347.前K个高频元素.md index d8eabef4..0d268d9b 100644 --- a/problems/0347.前K个高频元素.md +++ b/problems/0347.前K个高频元素.md @@ -79,8 +79,6 @@ ```CPP -// 时间复杂度：O(nlogk) -// 空间复杂度：O(n) class Solution { public: // 小顶堆 @@ -120,6 +118,10 @@ public: } }; ``` + +* 时间复杂度: O(nlogk) +* 空间复杂度: O(n) + # 拓展 大家对这个比较运算在建堆时是如何应用的，为什么左大于右就会建立小顶堆，反而建立大顶堆比较困惑。