From 89a0e147435ad10a4f1c6550d29795c48f76e53e Mon Sep 17 00:00:00 2001 From: youngyangyang04 <826123027@qq.com> Date: Fri, 27 Nov 2020 09:40:03 +0800 Subject: [PATCH] Update --- README.md | 5 ++ problems/0322.零钱兑换.md | 58 +++++++++++++++++++ ...1005.K次取反后最大化的数组和.md | 22 +++++++ problems/1221.分割平衡字符串.md | 19 ++++++ .../1403.非递增顺序的最小子序列.md | 25 ++++++++ problems/1518.换酒问题.md | 16 +++++ 6 files changed, 145 insertions(+) create mode 100644 problems/0322.零钱兑换.md create mode 100644 problems/1005.K次取反后最大化的数组和.md create mode 100644 problems/1221.分割平衡字符串.md create mode 100644 problems/1403.非递增顺序的最小子序列.md create mode 100644 problems/1518.换酒问题.md diff --git a/README.md b/README.md index 2e740298..a082a26d 100644 --- a/README.md +++ b/README.md @@ -173,6 +173,7 @@ * [关于贪心算法，你该了解这些！](https://mp.weixin.qq.com/s/O935TaoHE9Eexwe_vSbRAg) * [贪心算法：分发饼干](https://mp.weixin.qq.com/s/YSuLIAYyRGlyxbp9BNC1uw) * [贪心算法：摆动序列](https://mp.weixin.qq.com/s/Xytl05kX8LZZ1iWWqjMoHA) + * [贪心算法：最大子序和](https://mp.weixin.qq.com/s/DrjIQy6ouKbpletQr0g1Fg) * 动态规划 @@ -333,12 +334,16 @@ |[0973.最接近原点的K个点](https://github.com/youngyangyang04/leetcode/blob/master/problems/0973.最接近原点的K个点.md) |优先级队列 |中等|**优先级队列**| |[0977.有序数组的平方](https://github.com/youngyangyang04/leetcode/blob/master/problems/0977.有序数组的平方.md) |数组 |中等|**双指针** 还是比较巧妙的| |[1002.查找常用字符](https://github.com/youngyangyang04/leetcode/blob/master/problems/1002.查找常用字符.md) |栈 |简单|**栈**| +|[1005.K次取反后最大化的数组和](https://github.com/youngyangyang04/leetcode/blob/master/problems/1005.K次取反后最大化的数组和.md) |贪心/排序 |**贪心算法** 贪心基础题目| |[1047.删除字符串中的所有相邻重复项](https://github.com/youngyangyang04/leetcode/blob/master/problems/1047.删除字符串中的所有相邻重复项.md) |哈希表 |简单|**哈希表/数组**| |[1049.最后一块石头的重量II](https://github.com/youngyangyang04/leetcode/blob/master/problems/1049.最后一块石头的重量II.md) |动态规划 |中等|**01背包**| |[1207.独一无二的出现次数](https://github.com/youngyangyang04/leetcode/blob/master/problems/1207.独一无二的出现次数.md) |哈希表 |简单|**哈希** 两层哈希| +|[1221.分割平衡字符串](https://github.com/youngyangyang04/leetcode/blob/master/problems/1221.分割平衡字符串.md) |贪心 |简单|**贪心算法** 基础题目| |[1356.根据数字二进制下1的数目排序](https://github.com/youngyangyang04/leetcode/blob/master/problems/1356.根据数字二进制下1的数目排序.md) |位运算 |简单|**位运算** 巧妙的计算二进制中1的数量| |[1365.有多少小于当前数字的数字](https://github.com/youngyangyang04/leetcode/blob/master/problems/1365.有多少小于当前数字的数字.md) |数组、哈希表 |简单|**哈希** 从后遍历的技巧很不错| |[1382.将二叉搜索树变平衡](https://github.com/youngyangyang04/leetcode/blob/master/problems/1047.删除字符串中的所有相邻重复项.md) |二叉搜索树 |中等|**递归** **迭代** 98和108的组合题目| +|[1403.非递增顺序的最小子序列](https://github.com/youngyangyang04/leetcode/blob/master/problems/1403.非递增顺序的最小子序列.md) | 贪心算法|简单|**贪心算法** 贪心基础题目| +|[1518.换酒问题](https://github.com/youngyangyang04/leetcode/blob/master/problems/1518.换酒问题.md) | 贪心算法|简单|**贪心算法** 贪心基础题目| |[剑指Offer05.替换空格](https://github.com/youngyangyang04/leetcode/blob/master/problems/剑指Offer05.替换空格.md) |字符串 |简单|**双指针**| |[ 剑指Offer58-I.翻转单词顺序](https://github.com/youngyangyang04/leetcode/blob/master/problems/剑指Offer05.替换空格.md) |字符串 |简单|**模拟/双指针**| |[剑指Offer58-II.左旋转字符串](https://github.com/youngyangyang04/leetcode/blob/master/problems/剑指Offer58-II.左旋转字符串.md) |字符串 |简单|**反转操作**| diff --git a/problems/0322.零钱兑换.md b/problems/0322.零钱兑换.md new file mode 100644 index 00000000..879f8345 --- /dev/null +++ b/problems/0322.零钱兑换.md @@ -0,0 +1,58 @@ + +[1] 0 ，输出的是0，不是-1啊，这颗真是天坑j + +``` +// dp初始化很重要 +class Solution { +public: + int coinChange(vector& coins, int amount) { + //int dp[10003] = {0}; // 并没有给所有元素赋值0 + if (amount == 0) return 0; // 这个要注意 + vector dp(10003, 0); + // 不能这么初始化啊，[2147483647]，2 这种例子 直接gg，但是这种初始化有助于理解 + for (int i = 0; i < coins.size(); i++) { + if (coins[i] <= amount) // 还必须要加这个判断 + dp[coins[i]] = 1; + } + for (int i = 1; i <= amount; i++) { + for (int j = 0; j < coins.size(); j++) { + if (i - coins[j] >= 0 && dp[i - coins[j]]!=0 ) { + if (dp[i] == 0) dp[i] = dp[i - coins[j]] + 1; + else dp[i] = min(dp[i - coins[j]] + 1, dp[i]); + } + + + } + //for (int k = 0 ; k<= amount; k++) { + // cout << dp[k] << " "; + //} + //cout << endl; + } + if (dp[amount] == 0) return -1; + return dp[amount]; + + } +}; +``` + +这种标记d代码简短，但思路有点绕 +``` +class Solution { +public: + int coinChange(vector& coins, int amount) { + //int dp[10003] = {0}; // 并没有给所有元素赋值0 + // if (amount == 0) return 0; 这个都可以省略了，但很多同学不知道 还需要注意这个 + vector dp(10003, 0); + for (int i = 1; i <= amount; i++) { + dp[i] = INT_MAX; + for (int j = 0; j < coins.size(); j++) { + if (i - coins[j] >= 0 && dp[i - coins[j]]!=INT_MAX ) { + dp[i] = min(dp[i - coins[j]] + 1, dp[i]); + } + } + } + if (dp[amount] == INT_MAX) return -1; + return dp[amount]; + } +}; +``` diff --git a/problems/1005.K次取反后最大化的数组和.md b/problems/1005.K次取反后最大化的数组和.md new file mode 100644 index 00000000..2b98111e --- /dev/null +++ b/problems/1005.K次取反后最大化的数组和.md @@ -0,0 +1,22 @@ + +``` +class Solution { +static bool cmp(int a, int b) { + return abs(a) < abs(b); +} +public: + int largestSumAfterKNegations(vector& A, int K) { + sort(A.begin(), A.end(), cmp); + for (int i = A.size() - 1; i >= 0; i--) { + if (A[i] < 0 && K > 0) { + A[i] *= -1; + K--; + } + } + while (K--) A[0] *= -1; + int result = 0; + for (int a : A) result += a; + return result; + } +}; +``` diff --git a/problems/1221.分割平衡字符串.md b/problems/1221.分割平衡字符串.md new file mode 100644 index 00000000..757c483f --- /dev/null +++ b/problems/1221.分割平衡字符串.md @@ -0,0 +1,19 @@ + +这是贪心啊，LRLR 这本身就是平衡子串 , 但要LR这么分割，这是贪心 + + +``` +class Solution { +public: + int balancedStringSplit(string s) { + int result = 0; + int count = 0; + for (int i = 0; i < s.size(); i++) { + if (s[i] == 'R') count++; + else count--; + if (count == 0) result++; + } + return result; + } +}; +``` diff --git a/problems/1403.非递增顺序的最小子序列.md b/problems/1403.非递增顺序的最小子序列.md new file mode 100644 index 00000000..1957678c --- /dev/null +++ b/problems/1403.非递增顺序的最小子序列.md @@ -0,0 +1,25 @@ + +你说这是简单题吧，也是这就使用了贪心算法 + +``` +class Solution { +private: + static bool cmp(int a, int b) { + return a > b; + } +public: + vector minSubsequence(vector& nums) { + sort(nums.begin(), nums.end(), cmp); + int sum = 0; + for (int i = 0; i < nums.size(); i++) sum += nums[i]; + vector result; + int resultSum = 0; + for (int i = 0; i < nums.size(); i++) { + resultSum += nums[i]; + result.push_back(nums[i]); + if (resultSum > (sum - resultSum)) break; + } + return result; + } +}; +``` diff --git a/problems/1518.换酒问题.md b/problems/1518.换酒问题.md new file mode 100644 index 00000000..b72d7d2d --- /dev/null +++ b/problems/1518.换酒问题.md @@ -0,0 +1,16 @@ + +``` +// 这道题还是有陷阱啊，15 4 这个例子，答案应该是19 而不是18 +class Solution { +public: + int numWaterBottles(int numBottles, int numExchange) { + int result = numBottles; + while (numBottles / numExchange) { + result += numBottles / numExchange; + // 所以不是 numBottles = (numBottles / numExchange) + numBottles = (numBottles / numExchange) + (numBottles % numExchange); + } + return result; + } +}; +```