javascript - 字符串到整数 leetcode

Question

我在做下面的 leetcode 题

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: [−2³¹, 2³¹ − 1]. If the numerical value is out of the range of representable values, INT_MAX (2³¹ − 1) or INT_MIN (−2³¹) is returned.

提问链接:https://leetcode.com/problems/string-to-integer-atoi/

对于此输入 "-91283472332"，我不确定为什么他们期望以下输出 -2147483648 而不是 -91283472332

不确定，如果这相关但这是我的代码

/**
 * @param {string} str
 * @return {number}
 */
var myAtoi = function(str) {
    let i = 0
    let output = ''
    let nonWhiteCharacter = false 
    while (i<str.length) {
       const char = str[i]
       if (!char == " ") {
           if (char.toLowerCase() === char.toUpperCase()) {
            if (!nonWhiteCharacter) nonWhiteCharacter = true
               output = output + char
           }  
           if (!nonWhiteCharacter) return 0
       }
        i++
    }
    return output === null ? 0 : parseInt(output)
}

Answer 1

I am not sure why do they expect the following output -2147483648 instead of -91283472332

因为:

Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−2³¹, 2³¹ − 1]. If the numerical value is out of the range of representable values, INT_MAX (2³¹ − 1) or INT_MIN (−2³¹) is returned.

因此，如果提取的数字大于 2 ** 31 - 1，则返回的数字应该是 2 ** 31 - 1。

同理，如果提取的数字小于-(2 ** 31)，则返回-(2 ** 31)。

使用正则表达式可能会更容易:

const myAtoi = (str) => {
  const match = str.match(/^ *([+-]?\d+)/);
  if (!match) return;
  const num = Number(match[1]);
  return Math.max(
    Math.min(2 ** 31 - 1, num),
    -(2 ** 31)
  );
};

console.log(
  myAtoi('    123'),
  myAtoi('-456'),
  myAtoi('-9999999999999'),
  myAtoi('9999999999999')
);