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{ | ||
"cells": [ | ||
{ | ||
"cell_type": "markdown", | ||
"metadata": {}, | ||
"source": [ | ||
"难度:中等\n", | ||
"\n", | ||
"知识点:字符串、动态规划\n", | ||
"\n", | ||
"地址:[https://leetcode-cn.com/problems/longest-palindromic-substring/](https://leetcode-cn.com/problems/longest-palindromic-substring/)\n", | ||
"\n", | ||
"\n", | ||
"给定一个字符串 s,找到 s 中最长的回文子串。你可以假设 s 的最大长度为 1000。\n", | ||
"\n", | ||
"示例 1:\n", | ||
"\n", | ||
" 输入: \"babad\"\n", | ||
" 输出: \"bab\"\n", | ||
" 注意: \"aba\" 也是一个有效答案。\n", | ||
" \n", | ||
"示例 2:\n", | ||
"\n", | ||
" 输入: \"cbbd\"\n", | ||
" 输出: \"bb\"\n" | ||
] | ||
}, | ||
{ | ||
"cell_type": "code", | ||
"execution_count": null, | ||
"metadata": {}, | ||
"outputs": [], | ||
"source": [] | ||
} | ||
], | ||
"metadata": { | ||
"kernelspec": { | ||
"display_name": "Python 3", | ||
"language": "python", | ||
"name": "python3" | ||
}, | ||
"language_info": { | ||
"codemirror_mode": { | ||
"name": "ipython", | ||
"version": 3 | ||
}, | ||
"file_extension": ".py", | ||
"mimetype": "text/x-python", | ||
"name": "python", | ||
"nbconvert_exporter": "python", | ||
"pygments_lexer": "ipython3", | ||
"version": "3.7.6" | ||
} | ||
}, | ||
"nbformat": 4, | ||
"nbformat_minor": 4 | ||
} |
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{ | ||
"cells": [ | ||
{ | ||
"cell_type": "markdown", | ||
"metadata": {}, | ||
"source": [ | ||
"难度:中等\n", | ||
"\n", | ||
"知识点:数学、字符串\n", | ||
"\n", | ||
"地址:[https://leetcode-cn.com/problems/string-to-integer-atoi/](https://leetcode-cn.com/problems/string-to-integer-atoi/)\n", | ||
"\n", | ||
"\n", | ||
"请你来实现一个 atoi 函数,使其能将字符串转换成整数。\n", | ||
"\n", | ||
"首先,该函数会根据需要丢弃无用的开头空格字符,直到寻找到第一个非空格的字符为止。\n", | ||
"\n", | ||
"当我们寻找到的第一个非空字符为正或者负号时,则将该符号与之后面尽可能多的连续数字组合起来,作为该整数的正负号;假如第一个非空字符是数字,则直接将其与之后连续的数字字符组合起来,形成整数。\n", | ||
"\n", | ||
"该字符串除了有效的整数部分之后也可能会存在多余的字符,这些字符可以被忽略,它们对于函数不应该造成影响。\n", | ||
"\n", | ||
"注意:\n", | ||
" \n", | ||
" 假如该字符串中的第一个非空格字符不是一个有效整数字符、字符串为空或字符串仅包含空白字符时,则你的函数不需要进行转换。\n", | ||
" 在任何情况下,若函数不能进行有效的转换时,请返回 0。\n", | ||
"\n", | ||
"说明:\n", | ||
"\n", | ||
" 假设我们的环境只能存储 32 位大小的有符号整数,那么其数值范围为 [−2^31, 2^31 − 1]。如果数值超过这个范围,qing返回 INT_MAX (231 − 1) 或 INT_MIN (−231) 。\n", | ||
"\n", | ||
"示例 1:\n", | ||
"\n", | ||
" 输入: \"42\"\n", | ||
" 输出: 42\n", | ||
"\n", | ||
"示例 2:\n", | ||
"\n", | ||
" 输入: \" -42\"\n", | ||
" 输出: -42\n", | ||
" 解释: 第一个非空白字符为 '-', 它是一个负号。\n", | ||
" 我们尽可能将负号与后面所有连续出现的数字组合起来,最后得到 -42 。\n", | ||
"\n", | ||
"示例 3:\n", | ||
"\n", | ||
" 输入: \"4193 with words\"\n", | ||
" 输出: 4193\n", | ||
" 解释: 转换截止于数字 '3' ,因为它的下一个字符不为数字。\n", | ||
"\n", | ||
"示例 4:\n", | ||
"\n", | ||
" 输入: \"words and 987\"\n", | ||
" 输出: 0\n", | ||
" 解释: 第一个非空字符是 'w', 但它不是数字或正、负号。\n", | ||
" 因此无法执行有效的转换。\n", | ||
"\n", | ||
"示例 5:\n", | ||
"\n", | ||
" 输入: \"-91283472332\"\n", | ||
" 输出: -2147483648\n", | ||
" 解释: 数字 \"-91283472332\" 超过 32 位有符号整数范围。\n", | ||
" 因此返回 INT_MIN (−2^31) 。\n" | ||
] | ||
}, | ||
{ | ||
"cell_type": "code", | ||
"execution_count": 3, | ||
"metadata": {}, | ||
"outputs": [ | ||
{ | ||
"ename": "AssertionError", | ||
"evalue": "", | ||
"output_type": "error", | ||
"traceback": [ | ||
"\u001b[0;31m---------------------------------------------------------------------------\u001b[0m", | ||
"\u001b[0;31mAssertionError\u001b[0m Traceback (most recent call last)", | ||
"\u001b[0;32m<ipython-input-3-90c33c7ccd9f>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m 34\u001b[0m \u001b[0;32massert\u001b[0m \u001b[0ms\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mmyAtoi\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\" -42\"\u001b[0m\u001b[0;34m)\u001b[0m \u001b[0;34m==\u001b[0m \u001b[0;34m-\u001b[0m\u001b[0;36m42\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m 35\u001b[0m \u001b[0;32massert\u001b[0m \u001b[0ms\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mmyAtoi\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"4193 with words\"\u001b[0m\u001b[0;34m)\u001b[0m \u001b[0;34m==\u001b[0m \u001b[0;36m4193\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 36\u001b[0;31m \u001b[0;32massert\u001b[0m \u001b[0ms\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mmyAtoi\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"words and 987\"\u001b[0m\u001b[0;34m)\u001b[0m \u001b[0;34m==\u001b[0m \u001b[0;36m42\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m 37\u001b[0m \u001b[0;32massert\u001b[0m \u001b[0ms\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mmyAtoi\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"-91283472332\"\u001b[0m\u001b[0;34m)\u001b[0m \u001b[0;34m==\u001b[0m \u001b[0mMIN\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n", | ||
"\u001b[0;31mAssertionError\u001b[0m: " | ||
] | ||
} | ||
], | ||
"source": [ | ||
"from config import MAX\n", | ||
"from config import MIN\n", | ||
"\n", | ||
"NUMS = {\"1\", \"2\", '3', '4', '5', '6', '7', '8', '9', '0'}\n", | ||
"INTS = {\"1\", \"2\", '3', '4', '5', '6', '7', '8', '9'}\n", | ||
"class Solution:\n", | ||
" def myAtoi(self, s: str) -> int:\n", | ||
" \n", | ||
" singal = 1\n", | ||
" ans = 0\n", | ||
" for a in s:\n", | ||
" if a == ' ':\n", | ||
" continue\n", | ||
" if ans == 0 and a not in INTS:\n", | ||
" \n", | ||
" \n", | ||
" return ans\n", | ||
"\n", | ||
"s = Solution()\n", | ||
"assert s.myAtoi(\"42\") == 42\n", | ||
"assert s.myAtoi(\" -42\") == -42\n", | ||
"assert s.myAtoi(\"4193 with words\") == 4193\n", | ||
"assert s.myAtoi(\"words and 987\") == 42\n", | ||
"assert s.myAtoi(\"-91283472332\") == MIN" | ||
] | ||
} | ||
], | ||
"metadata": { | ||
"kernelspec": { | ||
"display_name": "Python 3", | ||
"language": "python", | ||
"name": "python3" | ||
}, | ||
"language_info": { | ||
"codemirror_mode": { | ||
"name": "ipython", | ||
"version": 3 | ||
}, | ||
"file_extension": ".py", | ||
"mimetype": "text/x-python", | ||
"name": "python", | ||
"nbconvert_exporter": "python", | ||
"pygments_lexer": "ipython3", | ||
"version": "3.7.6" | ||
} | ||
}, | ||
"nbformat": 4, | ||
"nbformat_minor": 4 | ||
} |
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{ | ||
"cells": [ | ||
{ | ||
"cell_type": "markdown", | ||
"metadata": {}, | ||
"source": [ | ||
"难度:简单\n", | ||
"\n", | ||
"知识点:字符串\n", | ||
"\n", | ||
"地址:[https://leetcode-cn.com/problems/longest-common-prefix/](https://leetcode-cn.com/problems/longest-common-prefix/)\n", | ||
"\n", | ||
"\n", | ||
"编写一个函数来查找字符串数组中的最长公共前缀。\n", | ||
"\n", | ||
"如果不存在公共前缀,返回空字符串 \"\"。\n", | ||
"\n", | ||
"示例 1:\n", | ||
"\n", | ||
" 输入: [\"flower\",\"flow\",\"flight\"]\n", | ||
" 输出: \"fl\"\n", | ||
"示例 2:\n", | ||
"\n", | ||
" 输入: [\"dog\",\"racecar\",\"car\"]\n", | ||
" 输出: \"\"\n", | ||
" 解释: 输入不存在公共前缀。\n", | ||
"说明:\n", | ||
"\n", | ||
" 所有输入只包含小写字母 a-z 。\n" | ||
] | ||
}, | ||
{ | ||
"cell_type": "code", | ||
"execution_count": null, | ||
"metadata": {}, | ||
"outputs": [], | ||
"source": [ | ||
"class Solution:\n", | ||
" def longestCommonPrefix(self, strs) -> str:\n", | ||
" strs.sort(key = lambda x: len(x))\n", | ||
" res = strs[0]\n", | ||
" i = len(res)\n", | ||
" while i >= 0:\n", | ||
" for s in strs[1:]:\n", | ||
" if not s.startswith(res[:i]):\n", | ||
" i -= 1\n", | ||
" break\n", | ||
" if i < 0:\n", | ||
" return ''\n", | ||
" return res[:i]\n", | ||
" \n", | ||
" \n", | ||
"\n", | ||
"s = Solution()\n", | ||
"assert s.longestCommonPrefix([\"flower\",\"flow\",\"flight\"]) == 'fl'\n", | ||
"assert s.longestCommonPrefix([\"dog\",\"racecar\",\"car\"]) == ''" | ||
] | ||
} | ||
], | ||
"metadata": { | ||
"kernelspec": { | ||
"display_name": "Python 3", | ||
"language": "python", | ||
"name": "python3" | ||
}, | ||
"language_info": { | ||
"codemirror_mode": { | ||
"name": "ipython", | ||
"version": 3 | ||
}, | ||
"file_extension": ".py", | ||
"mimetype": "text/x-python", | ||
"name": "python", | ||
"nbconvert_exporter": "python", | ||
"pygments_lexer": "ipython3", | ||
"version": "3.7.6" | ||
} | ||
}, | ||
"nbformat": 4, | ||
"nbformat_minor": 4 | ||
} |
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{ | ||
"cells": [ | ||
{ | ||
"cell_type": "markdown", | ||
"metadata": {}, | ||
"source": [ | ||
"难度:简单\n", | ||
"\n", | ||
"地址:[https://leetcode-cn.com/problems/two-sum/](https://leetcode-cn.com/problems/two-sum/)\n", | ||
"\n", | ||
"给定一个整数数组 nums 和一个目标值 target,请你在该数组中找出和为目标值的那 两个 整数,并返回他们的数组下标。\n", | ||
"\n", | ||
"你可以假设每种输入只会对应一个答案。但是,你不能重复利用这个数组中同样的元素。\n", | ||
"\n", | ||
"示例:\n", | ||
"\n", | ||
" 给定 nums = [2, 7, 11, 15], target = 9\n", | ||
" 因为 nums[0] + nums[1] = 2 + 7 = 9\n", | ||
" 所以返回 [0, 1]\n" | ||
] | ||
}, | ||
{ | ||
"cell_type": "code", | ||
"execution_count": 7, | ||
"metadata": {}, | ||
"outputs": [ | ||
{ | ||
"data": { | ||
"text/plain": [ | ||
"[0, 1]" | ||
] | ||
}, | ||
"execution_count": 7, | ||
"metadata": {}, | ||
"output_type": "execute_result" | ||
} | ||
], | ||
"source": [ | ||
"class Solution:\n", | ||
" def twoSum(self, nums, target):\n", | ||
" '''\n", | ||
" 两遍哈希表 时间复杂度 O(n)\n", | ||
" 执行用时 : 56 ms, 在Two Sum的Python3提交中击败了89.57% 的用户\n", | ||
" 内存消耗 : 14.7 MB, 在Two Sum的Python3提交中击败了7.13% 的用户\n", | ||
" '''\n", | ||
" length = len(nums)\n", | ||
" m = {}\n", | ||
" for i in range(length):\n", | ||
" m[nums[i]] = i\n", | ||
" for i in range(length):\n", | ||
" x = nums[i]\n", | ||
" y = target - x\n", | ||
" if y in m:\n", | ||
" return [i, m[y]]\n", | ||
" \n", | ||
" \n", | ||
"\n", | ||
"s = Solution()\n", | ||
"s.twoSum([2, 7, 11, 15], 9)" | ||
] | ||
}, | ||
{ | ||
"cell_type": "code", | ||
"execution_count": 8, | ||
"metadata": {}, | ||
"outputs": [ | ||
{ | ||
"data": { | ||
"text/plain": [ | ||
"[0, 1]" | ||
] | ||
}, | ||
"execution_count": 8, | ||
"metadata": {}, | ||
"output_type": "execute_result" | ||
} | ||
], | ||
"source": [ | ||
"class Solution:\n", | ||
" def twoSum(self, nums, target):\n", | ||
" '''\n", | ||
" 一遍哈希表 时间复杂度 O(n)\n", | ||
" 执行用时 : 44 ms, 在Two Sum的Python3提交中击败了99.33% 的用户\n", | ||
" 内存消耗 : 14 MB, 在Two Sum的Python3提交中击败了56.25% 的用户\n", | ||
" '''\n", | ||
" m = {}\n", | ||
" for i in range(len(nums)):\n", | ||
" x = nums[i]\n", | ||
" y = target - x\n", | ||
" if y in m:\n", | ||
" return [m[y], i]\n", | ||
" m[x] = i\n", | ||
" \n", | ||
"\n", | ||
"s = Solution()\n", | ||
"s.twoSum([2, 7, 11, 15], 9)" | ||
] | ||
} | ||
], | ||
"metadata": { | ||
"kernelspec": { | ||
"display_name": "Python 3", | ||
"language": "python", | ||
"name": "python3" | ||
}, | ||
"language_info": { | ||
"codemirror_mode": { | ||
"name": "ipython", | ||
"version": 3 | ||
}, | ||
"file_extension": ".py", | ||
"mimetype": "text/x-python", | ||
"name": "python", | ||
"nbconvert_exporter": "python", | ||
"pygments_lexer": "ipython3", | ||
"version": "3.7.6" | ||
} | ||
}, | ||
"nbformat": 4, | ||
"nbformat_minor": 4 | ||
} |
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