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SakuraSnow

一只前端咸鱼
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  • 数据结构

  • Leetcode

    • 001-Two Sum[两数之和]
    • 002-Add Two Numbers[两数相加].md
    • 003-Longest Substring Without Repeating Characters[无重复字符的最长子串]
    • 004-Reverse-integer[整数反转]
    • 008-String to Integer (atoi)[字符串转整数]
      • 009-Palindrome Number[回文数]
    • 算法
    • Leetcode
    SakuraSnow
    2022-03-10

    008-String to Integer (atoi)[字符串转整数]

    # 题目

    Implement the myAtoi(string s) function, which converts a string to a 32-bit signed integer (similar to C/C++'s atoi function).

    The algorithm for myAtoi(string s) is as follows:

    1. Read in and ignore any leading whitespace.
    2. Check if the next character (if not already at the end of the string) is '-' or '+'. Read this character in if it is either. This determines if the final result is negative or positive respectively. Assume the result is positive if neither is present.
    3. Read in next the characters until the next non-digit character or the end of the input is reached. The rest of the string is ignored.
    4. Convert these digits into an integer (i.e. "123" -> 123, "0032" -> 32). If no digits were read, then the integer is 0. Change the sign as necessary (from step 2).
    5. If the integer is out of the 32-bit signed integer range [-231, 231 - 1], then clamp the integer so that it remains in the range. Specifically, integers less than -231 should be clamped to -231, and integers greater than 231 - 1 should be clamped to 231 - 1.
    6. Return the integer as the final result.

    # example

    Input: s = "42"
    Output: 42
    Explanation: The underlined characters are what is read in, the caret is the current reader position.
    Step 1: "42" (no characters read because there is no leading whitespace)
             ^
    Step 2: "42" (no characters read because there is neither a '-' nor '+')
             ^
    Step 3: "42" ("42" is read in)
               ^
    The parsed integer is 42.
    Since 42 is in the range [-231, 231 - 1], the final result is 42.Given a signed 32-bit integer x, return x with its digits reversed. If reversing x causes the value to go outside the signed 32-bit integer range [-231, 231 - 1], then return 0.
    
    Assume the environment does not allow you to store 64-bit integers (signed or unsigned).
    
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    Input: s = "   -42"
    Output: -42
    Explanation:
    Step 1: "   -42" (leading whitespace is read and ignored)
                ^
    Step 2: "   -42" ('-' is read, so the result should be negative)
                 ^
    Step 3: "   -42" ("42" is read in)
                   ^
    The parsed integer is -42.
    Since -42 is in the range [-231, 231 - 1], the final result is -42.Input: x = 123
    Output: 321
    
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    nput: s = "4193 with words"
    Output: 4193
    Explanation:
    Step 1: "4193 with words" (no characters read because there is no leading whitespace)
             ^
    Step 2: "4193 with words" (no characters read because there is neither a '-' nor '+')
             ^
    Step 3: "4193 with words" ("4193" is read in; reading stops because the next character is a non-digit)
                 ^
    The parsed integer is 4193.
    Since 4193 is in the range [-231, 231 - 1], the final result is 4193.Input: x = -123
    Output: -321
    
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    # 我的思路

    正则摆烂

    function myAtoi(s: string): number {
        // 匹配: 0个以上的空白 可能有的+- 一个及以上的数字
        let match = s.match(/^[\s]*[+-]?[\d]+/);
        let res = match ? Number(match) : 0;
        let limit = 2 ** 31;
        // 截断
        if (res > (limit - 1)) {
            res = limit - 1;
        } else if (res < -limit) {
            res = -limit;
        }
        // 返回
        return res;
    };
    
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    # 最优解

    花里胡哨,不如正则

    #算法#Leetcode#正则
    上次更新: 2022/03/10, 13:34:30
    004-Reverse-integer[整数反转]
    009-Palindrome Number[回文数]

    ← 004-Reverse-integer[整数反转] 009-Palindrome Number[回文数]→

    最近更新
    01
    009-Palindrome Number[回文数]
    03-10
    02
    004-Reverse-integer[整数反转]
    03-09
    03
    003-Longest Substring Without Repeating Characters[无重复字符的最长子串]
    03-09
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