ARTS

Sun, 11 Nov 2018 07:04:21 +0000

ARTS

A (Algotithm) 至少做一个leetcode的算法题
R (Review) 阅读并点评一篇英文的技术文章
T (Tip) 学习一个技术技巧
S (Share) 分享一篇有观点和思考的技术文章

每周一次，坚持一年

Algorithm

Description https://leetcode.com/problems/string-to-integer-atoi/

Implement atoi which converts a string to an integer.

The function first discards as many whitespace characters as necessary until the first non-whitespace character is found. Then, starting from this character, takes an optional initial plus or minus sign followed by as many numerical digits as possible, and interprets them as a numerical value.

The string can contain additional characters after those that form the integral number, which are ignored and have no effect on the behavior of this function.

If the first sequence of non-whitespace characters in str is not a valid integral number, or if no such sequence exists because either str is empty or it contains only whitespace characters, no conversion is performed.

If no valid conversion could be performed, a zero value is returned.

Note:

Only the space character ' ' is considered as whitespace character.
Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−2^31,  2^31 − 1]. If the numerical value is out of the range of representable values, INT_MAX (2^31 − 1) or INT_MIN (−2^31) is returned.
Example 1:

Input: "42"
Output: 42
Example 2:

Input: "   -42"
Output: -42
Explanation: The first non-whitespace character is '-', which is the minus sign.
             Then take as many numerical digits as possible, which gets 42.
Example 3:

Input: "4193 with words"
Output: 4193
Explanation: Conversion stops at digit '3' as the next character is not a numerical digit.
Example 4:

Input: "words and 987"
Output: 0
Explanation: The first non-whitespace character is 'w', which is not a numerical
             digit or a +/- sign. Therefore no valid conversion could be performed.
Example 5:

Input: "-91283472332"
Output: -2147483648
Explanation: The number "-91283472332" is out of the range of a 32-bit signed integer.
             Thefore INT_MIN (−2^31) is returned.

Solution

/**
 * @param {string} str
 * @return {number}
 * https://leetcode.com/problems/string-to-integer-atoi/
 */
var myAtoi = function(str) {
    var result = parseInt(str, 10);
    if (isNaN(result)) {
        return 0;
    }
    if (result >= Math.pow(2, 31)) {
        return Math.pow(2, 31) - 1;
    } else if (result < -Math.pow(2, 31)) {
        return -Math.pow(2, 31);
    }
    return result;
};

console.log(myAtoi('42'), 42);
console.log(myAtoi('+-42'), 0);
console.log(myAtoi('     -42'), -42);
console.log(myAtoi('4193 with words'), 4193);
console.log(myAtoi('words and 987'), 0);
console.log(myAtoi('-91283472332'), -2147483648);

/**
 * https://segmentfault.com/a/1190000010571914
 * JavaScript 实现 parseInt()
 */

Review

Comparing Flow with TypeScript https://medium.com/the-web-tub/comparing-flow-with-typescript-6a8ff7fd4cbb

这篇文章指在比较 Flow 与 Typescript 的异同。

Flow 和 Typescript 皆是使 JavaScript 可以以静态类型的方式去书写，即可使用静态类型语音的优势。但是 Flow 比 Typescript 更简单，开箱即用、对库/框架/编译器更好的兼容性、它有能力保持 JS 的纯粹。只在项目开头添加 // @flow 即可。

Tip

JS: Array.reverse() vs. for and while loops https://jsperf.com/js-array-reverse-vs-while-loop/66

我们可以从这篇文章获知 JS 的数组颠倒使用 for 循环的 swap half、XOR swap half 效率最高。

css 的 white-space

换行符	空格和 Tab	文本超出容器宽度	-
nomal	忽略	折叠	换行
nowrap	忽略	折叠	不换行
pre	换行	保持原样	不换行
pre-wrap	换行	保持原样	换行
pre-line	换行	折叠	换行

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