From 7cc24bd8eccb716dcc969b1c0d96189dc8f3fc4e Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 20:49:36 +0800 Subject: [PATCH 01/13] =?UTF-8?q?Update=200707.=E8=AE=BE=E8=AE=A1=E9=93=BE?= =?UTF-8?q?=E8=A1=A8.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0707.设计链表.md | 71 +++++++++++++++++++++++++++++++++++ 1 file changed, 71 insertions(+) diff --git a/problems/0707.设计链表.md b/problems/0707.设计链表.md index f98051c9..93133b55 100644 --- a/problems/0707.设计链表.md +++ b/problems/0707.设计链表.md @@ -157,7 +157,78 @@ private: Java： +```Java +class MyLinkedList { + //size存储链表元素的个数 + int size; + //虚拟头结点 + ListNode head; + //初始化链表 + public MyLinkedList() { + size = 0; + head = new ListNode(0); + } + + //获取第index个节点的数值 + public int get(int index) { + //如果index非法，返回-1 + if (index < 0 || index >= size) { + return -1; + } + ListNode currentNode = head; + //包含一个虚拟头节点，所以查找第 index+1 个节点 + for (int i = 0; i <= index; i++) { + currentNode = currentNode.next; + } + return currentNode.val; + } + + //在链表最前面插入一个节点 + public void addAtHead(int val) { + addAtIndex(0, val); + } + + //在链表的最后插入一个节点 + public void addAtTail(int val) { + addAtIndex(size, val); + } + + // 在第 index 个节点之前插入一个新节点，例如index为0，那么新插入的节点为链表的新头节点。 + // 如果 index 等于链表的长度，则说明是新插入的节点为链表的尾结点 + // 如果 index 大于链表的长度，则返回空 + public void addAtIndex(int index, int val) { + if (index > size) { + return; + } + if (index < 0) { + index = 0; + } + size++; + //找到要插入节点的前驱 + ListNode pred = head; + for (int i = 0; i < index; i++) { + pred = pred.next; + } + ListNode toAdd = new ListNode(val); + toAdd.next = pred.next; + pred.next = toAdd; + } + + //删除第index个节点 + public void deleteAtIndex(int index) { + if (index < 0 || index >= size) { + return; + } + size--; + ListNode pred = head; + for (int i = 0; i < index; i++) { + pred = pred.next; + } + pred.next = pred.next.next; + } +} +``` Python： From 52ebd0882152d8994348b46de28bfd40cce87f7b Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 20:51:36 +0800 Subject: [PATCH 02/13] =?UTF-8?q?Update=200746.=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 --- problems/0746.使用最小花费爬楼梯.md | 21 +++++++++++++++++++- 1 file changed, 20 insertions(+), 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 e87f782c..b8158205 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 @@ -203,7 +203,26 @@ public: Java： - +```Java +class Solution { + public int minCostClimbingStairs(int[] cost) { + if (cost == null || cost.length == 0) { + return 0; + } + if (cost.length == 1) { + return cost[0]; + } + int[] dp = new int[cost.length]; + dp[0] = cost[0]; + dp[1] = cost[1]; + for (int i = 2; i < cost.length; i++) { + dp[i] = Math.min(dp[i - 1], dp[i - 2]) + cost[i]; + } + //最后一步，如果是由倒数第二步爬，则最后一步的体力花费可以不用算 + return Math.min(dp[cost.length - 1], dp[cost.length - 2]); + } +} +``` Python： From ef491ed5df698b79bfc0075bbd6dc811b53abe51 Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 20:54:22 +0800 Subject: [PATCH 03/13] =?UTF-8?q?Update=200518.=E9=9B=B6=E9=92=B1=E5=85=91?= =?UTF-8?q?=E6=8D=A2II.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0518.零钱兑换II.md | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/problems/0518.零钱兑换II.md b/problems/0518.零钱兑换II.md index 46e52cc0..15c9d7d0 100644 --- a/problems/0518.零钱兑换II.md +++ b/problems/0518.零钱兑换II.md @@ -188,7 +188,22 @@ public: Java： - +```Java +class Solution { + public int change(int amount, int[] coins) { + //递推表达式 + int[] dp = new int[amount + 1]; + //初始化dp数组，表示金额为0时只有一种情况，也就是什么都不装 + dp[0] = 1; + for (int i = 0; i < coins.length; i++) { + for (int j = coins[i]; j <= amount; j++) { + dp[j] += dp[j - coins[i]]; + } + } + return dp[amount]; + } +} +``` Python： From e79b6ac44437af05fe16a9d7921d18a6c28cf514 Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 20:55:32 +0800 Subject: [PATCH 04/13] =?UTF-8?q?Update=200474.=E4=B8=80=E5=92=8C=E9=9B=B6?= =?UTF-8?q?.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0474.一和零.md | 28 +++++++++++++++++++++++++++- 1 file changed, 27 insertions(+), 1 deletion(-) diff --git a/problems/0474.一和零.md b/problems/0474.一和零.md index 7970c38e..4ec5fd4d 100644 --- a/problems/0474.一和零.md +++ b/problems/0474.一和零.md @@ -161,7 +161,33 @@ public: Java： - +```Java +class Solution { + public int findMaxForm(String[] strs, int m, int n) { + //dp[i][j]表示i个0和j个1时的最大子集 + int[][] dp = new int[m + 1][n + 1]; + int oneNum, zeroNum; + for (String str : strs) { + oneNum = 0; + zeroNum = 0; + for (char ch : str.toCharArray()) { + if (ch == '0') { + zeroNum++; + } else { + oneNum++; + } + } + //倒序遍历 + for (int i = m; i >= zeroNum; i--) { + for (int j = n; j >= oneNum; j--) { + dp[i][j] = Math.max(dp[i][j], dp[i - zeroNum][j - oneNum] + 1); + } + } + } + return dp[m][n]; + } +} +``` Python： From ee62a698960280e3a89950bd193621c71bbd67df Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 20:56:06 +0800 Subject: [PATCH 05/13] =?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 --- problems/0454.四数相加II.md | 31 ++++++++++++++++++++++++++++++- 1 file changed, 30 insertions(+), 1 deletion(-) diff --git a/problems/0454.四数相加II.md b/problems/0454.四数相加II.md index 71dcc1ae..a2ef928b 100644 --- a/problems/0454.四数相加II.md +++ b/problems/0454.四数相加II.md @@ -88,7 +88,36 @@ public: Java： - +```Java +class Solution { + public int fourSumCount(int[] nums1, int[] nums2, int[] nums3, int[] nums4) { + Map map = new HashMap<>(); + int temp; + int res = 0; + //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); + } else { + map.put(temp, 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); + } + } + } + return res; + } +} +``` Python： From 97f717d9990c7e7ff2174098f31a2771471e6dfd Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 20:56:48 +0800 Subject: [PATCH 06/13] =?UTF-8?q?Update=200416.=E5=88=86=E5=89=B2=E7=AD=89?= =?UTF-8?q?=E5=92=8C=E5=AD=90=E9=9B=86.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0416.分割等和子集.md | 34 +++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/problems/0416.分割等和子集.md b/problems/0416.分割等和子集.md index 257c4d7d..789a7fb5 100644 --- a/problems/0416.分割等和子集.md +++ b/problems/0416.分割等和子集.md @@ -185,7 +185,41 @@ public: Java： +```Java +class Solution { + public boolean canPartition(int[] nums) { + int sum = 0; + for (int i : nums) { + sum += i; + } + if ((sum & 1) == 1) { + return false; + } + int length = nums.length; + int target = sum >> 1; + //dp[j]表示前i个元素可以找到相加等于j情况 + boolean[] dp = new boolean[target + 1]; + //对于第一个元素，只有当j=nums[0]时，才恰好填充满 + if (nums[0] <= target) { + dp[nums[0]] = true; + } + for (int i = 1; i < length; i++) { + //j由右往左直到nums[i] + for (int j = target; j >= nums[i]; j--) { + //只有两种情况，要么放，要么不放 + //取其中的TRUE值 + dp[j] = dp[j] || dp[j - nums[i]]; + } + //一旦满足，结束，因为只需要找到一组值即可 + if (dp[target]) { + return dp[target]; + } + } + return dp[target]; + } +} +``` Python： From b55d593cb726630f3800b16256161a53a554ebcc Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 20:57:14 +0800 Subject: [PATCH 07/13] =?UTF-8?q?Update=200383.=E8=B5=8E=E9=87=91=E4=BF=A1?= =?UTF-8?q?.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0383.赎金信.md | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/problems/0383.赎金信.md b/problems/0383.赎金信.md index ca9b6061..742bfdc3 100644 --- a/problems/0383.赎金信.md +++ b/problems/0383.赎金信.md @@ -111,7 +111,31 @@ public: Java： +```Java +class Solution { + public boolean canConstruct(String ransomNote, String magazine) { + //记录杂志字符串出现的次数 + int[] arr = new int[26]; + int temp; + for (int i = 0; i < magazine.length(); i++) { + temp = magazine.charAt(i) - 'a'; + arr[temp]++; + } + for (int i = 0; i < ransomNote.length(); i++) { + temp = ransomNote.charAt(i) - 'a'; + //对于金信中的每一个字符都在数组中查找 + //找到相应位减一，否则找不到返回false + if (arr[temp] > 0) { + arr[temp]--; + } else { + return false; + } + } + return true; + } +} +``` Python： From 17f24ae62179b550b439ee14b595a03b6a46f53b Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 20:57:43 +0800 Subject: [PATCH 08/13] =?UTF-8?q?Update=200377.=E7=BB=84=E5=90=88=E6=80=BB?= =?UTF-8?q?=E5=92=8C=E2=85=A3.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0377.组合总和Ⅳ.md | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/problems/0377.组合总和Ⅳ.md b/problems/0377.组合总和Ⅳ.md index b0b83718..8f8cfd86 100644 --- a/problems/0377.组合总和Ⅳ.md +++ b/problems/0377.组合总和Ⅳ.md @@ -147,7 +147,23 @@ C++测试用例有超过两个树相加超过int的数据，所以需要在if里 Java： +```Java +class Solution { + public int combinationSum4(int[] nums, int target) { + int[] dp = new int[target + 1]; + dp[0] = 1; + for (int i = 0; i <= target; i++) { + for (int j = 0; j < nums.length; j++) { + if (i >= nums[j]) { + dp[i] += dp[i - nums[j]]; + } + } + } + return dp[target]; + } +} +``` Python： From a8537880cf151729b5e6145f323bb2f7957de64a Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 20:58:17 +0800 Subject: [PATCH 09/13] =?UTF-8?q?Update=200322.=E9=9B=B6=E9=92=B1=E5=85=91?= =?UTF-8?q?=E6=8D=A2.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0322.零钱兑换.md | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) diff --git a/problems/0322.零钱兑换.md b/problems/0322.零钱兑换.md index fbb9c6df..e67695d8 100644 --- a/problems/0322.零钱兑换.md +++ b/problems/0322.零钱兑换.md @@ -181,7 +181,31 @@ public: Java： - +```Java +class Solution { + public int coinChange(int[] coins, int amount) { + int max = Integer.MAX_VALUE; + int[] dp = new int[amount + 1]; + //初始化dp数组为最大值 + for (int j = 0; j < dp.length; j++) { + dp[j] = max; + } + //当金额为0时需要的硬币数目为0 + dp[0] = 0; + for (int i = 0; i < coins.length; i++) { + //正序遍历：完全背包每个硬币可以选择多次 + for (int j = coins[i]; j <= amount; j++) { + //只有dp[j-coins[i]]不是初始最大值时，该位才有选择的必要 + if (dp[j - coins[i]] != max) { + //选择硬币数目最小的情况 + dp[j] = Math.min(dp[j], dp[j - coins[i]] + 1); + } + } + } + return dp[amount] == max ? -1 : dp[amount]; + } +} +``` Python： From cbc001a25eb5c6a33c36a8f5a99cc28d6c60a195 Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 20:58:47 +0800 Subject: [PATCH 10/13] =?UTF-8?q?Update=200055.=E8=B7=B3=E8=B7=83=E6=B8=B8?= =?UTF-8?q?=E6=88=8F.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0055.跳跃游戏.md | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) diff --git a/problems/0055.跳跃游戏.md b/problems/0055.跳跃游戏.md index 0cad1fa7..179ac246 100644 --- a/problems/0055.跳跃游戏.md +++ b/problems/0055.跳跃游戏.md @@ -86,7 +86,25 @@ public: Java： - +```Java +class Solution { + public boolean canJump(int[] nums) { + if (nums.length == 1) { + return true; + } + //覆盖范围 + int coverRange = nums[0]; + //在覆盖范围内更新最大的覆盖范围 + for (int i = 0; i <= coverRange; i++) { + coverRange = Math.max(coverRange, i + nums[i]); + if (coverRange >= nums.length - 1) { + return true; + } + } + return false; + } +} +``` Python： From fbd4dd9549b75daf60d1b741c534e5c1e6786eb5 Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 20:59:19 +0800 Subject: [PATCH 11/13] =?UTF-8?q?Update=200045.=E8=B7=B3=E8=B7=83=E6=B8=B8?= =?UTF-8?q?=E6=88=8FII.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0045.跳跃游戏II.md | 31 ++++++++++++++++++++++++++++++- 1 file changed, 30 insertions(+), 1 deletion(-) diff --git a/problems/0045.跳跃游戏II.md b/problems/0045.跳跃游戏II.md index 2def83a9..b8e369e6 100644 --- a/problems/0045.跳跃游戏II.md +++ b/problems/0045.跳跃游戏II.md @@ -143,7 +143,36 @@ public: Java： - +```Java +class Solution { + public int jump(int[] nums) { + if (nums == null || nums.length == 0 || nums.length == 1) { + return 0; + } + //记录跳跃的次数 + int count=0; + //当前的覆盖最大区域 + int curDistance = 0; + //最大的覆盖区域 + int maxDistance = 0; + for (int i = 0; i < nums.length; i++) { + //在可覆盖区域内更新最大的覆盖区域 + maxDistance = Math.max(maxDistance,i+nums[i]); + //说明当前一步，再跳一步就到达了末尾 + if (maxDistance>=nums.length-1){ + count++; + break; + } + //走到当前覆盖的最大区域时，更新下一步可达的最大区域 + if (i==curDistance){ + curDistance = maxDistance; + count++; + } + } + return count; + } +} +``` Python： From be33e5b3c92f9c3d228ff15402a7c6913d599337 Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 20:59:49 +0800 Subject: [PATCH 12/13] =?UTF-8?q?Update=200040.=E7=BB=84=E5=90=88=E6=80=BB?= =?UTF-8?q?=E5=92=8CII.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0040.组合总和II.md | 36 +++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) diff --git a/problems/0040.组合总和II.md b/problems/0040.组合总和II.md index ffcbe212..50898016 100644 --- a/problems/0040.组合总和II.md +++ b/problems/0040.组合总和II.md @@ -255,7 +255,43 @@ public: Java： +```Java +class Solution { + List> lists = new ArrayList<>(); + Deque deque = new LinkedList<>(); + int sum = 0; + public List> combinationSum2(int[] candidates, int target) { + //为了将重复的数字都放到一起，所以先进行排序 + Arrays.sort(candidates); + //加标志数组，用来辅助判断同层节点是否已经遍历 + boolean[] flag = new boolean[candidates.length]; + backTracking(candidates, target, 0, flag); + return lists; + } + + public void backTracking(int[] arr, int target, int index, boolean[] flag) { + if (sum == target) { + lists.add(new ArrayList(deque)); + return; + } + for (int i = index; i < arr.length && arr[i] + sum <= target; i++) { + //出现重复节点，同层的第一个节点已经被访问过，所以直接跳过 + if (i > 0 && arr[i] == arr[i - 1] && !flag[i - 1]) { + continue; + } + flag[i] = true; + sum += arr[i]; + deque.push(arr[i]); + //每个节点仅能选择一次，所以从下一位开始 + backTracking(arr, target, i + 1, flag); + int temp = deque.pop(); + flag[i] = false; + sum -= temp; + } + } +} +``` Python： From 5f1fa81305a41565791978aa91d6e16a4f820f80 Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 21:00:14 +0800 Subject: [PATCH 13/13] =?UTF-8?q?Update=200039.=E7=BB=84=E5=90=88=E6=80=BB?= =?UTF-8?q?=E5=92=8C.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0039.组合总和.md | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/problems/0039.组合总和.md b/problems/0039.组合总和.md index f983a994..ab118ee0 100644 --- a/problems/0039.组合总和.md +++ b/problems/0039.组合总和.md @@ -236,7 +236,39 @@ public: Java： +```Java +class Solution { + List> lists = new ArrayList<>(); + Deque deque = new LinkedList<>(); + public List> combinationSum3(int k, int n) { + int[] arr = new int[]{1, 2, 3, 4, 5, 6, 7, 8, 9}; + backTracking(arr, n, k, 0); + return lists; + } + + public void backTracking(int[] arr, int n, int k, int startIndex) { + //如果 n 小于0，没必要继续本次递归，已经不符合要求了 + if (n < 0) { + return; + } + if (deque.size() == k) { + if (n == 0) { + lists.add(new ArrayList(deque)); + } + return; + } + for (int i = startIndex; i < arr.length - (k - deque.size()) + 1; i++) { + deque.push(arr[i]); + //减去当前元素 + n -= arr[i]; + backTracking(arr, n, k, i + 1); + //恢复n + n += deque.pop(); + } + } +} +``` Python：