8. String to Integer (atoi)

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

JavaScript

/**
 * @param {string} str
 * @return {number}
 */
var myAtoi = function(str) {
  const INT_MAX = 2147483647
  const INT_MIN = -2147483648

  if (!str) {
    return 0
  }

  var i = 0
  var result = 0
  var sign = 1

  str = str.trim()

  if (str[i] === '+') {
    i++
  } else if (str[i] === '-') {
    sign = -1
    i++
  }

  while (i < str.length && str[i] >= '0' && str[i] <= '9') {
    let num = +str[i]

    if (result > (INT_MAX - num) / 10) {
      return sign > 0 ? INT_MAX : INT_MIN
    }

    result = result * 10 + num
    i++
  }

  return sign * result
}

Python

class Solution(object):

    def myAtoi(self, s):
        """
        :type s: str
        :rtype: int
        """
        INT_MAX, INT_MIN = 2147483647, -2147483648
        if not s:
            return 0
        i, result, sign = 0, 0, 1
        s = s.strip()

        if s[i] == '+':
            i += 1
        elif s[i] == '-':
            sign = -1
            i += 1

        while i < len(s) and s[i] >= '0' and s[i] <= '9':
            num = int(s[i])
            if result > (INT_MAX - num) / 10:
                return INT_MAX if sign > 0 else INT_MIN
            result = result * 10 + num
            i += 1

        return sign * result

Go

import "math"

func myAtoi(str string) int {
	if len(str) == 0 {
		return 0
	}

	var result int32 = 0
	var sign int32 = 1
	i := 0

	for str[i] == ' ' {
		i++
	}

	if str[i] == '+' {
		i++
	} else if str[i] == '-' {
		sign = -1
		i++
	}

	for i < len(str) && str[i] >= '0' && str[i] <= '9' {
		num := int32(str[i] - '0')

		if result > (math.MaxInt32-num)/10 {
			if sign > 0 {
				return math.MaxInt32
			}
			return math.MinInt32
		}

		result = result*10 + num
		i++
	}

	return int(sign * result)
}