atoi.js

//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:

// Read in and ignore any leading whitespace.
// 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.
// 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.
// 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).
// 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.
// Return the integer as the final result.
// Note:

// Only the space character ' ' is considered a whitespace character.
// Do not ignore any characters other than the leading whitespace or the rest of the string after the digit
/**
 * @param {string} s
 * @return {number}
 */
var myAtoi = function (s) {
  let str = s.trim();
  if (!str) return 0;
  let isPositive = 1; 
  let result = 0;
  let i = 0;
  // Check for leading '+' or '-' sign
  if (str[i] === "+") {
    isPositive = 1;
    i++;
  } else if (str[i] === "-") {
    isPositive = 0;
    i++;
  }
  while (i < str.length) {
    let value = str.charCodeAt(i) - 48; // Convert character to integer value
    if (value > 9 || value < 0) break; // Stop if non-numeric character encountered
    // Check for overflow
    if (result > 2 ** 31 - 1 || result > (2 ** 31 - 1 - value) / 10) {
      return isPositive ? 2 ** 31 - 1 : -(2 ** 31);
    } else {
      result = result * 10 + value;
    }
    i++;
  }
  return isPositive ? result : -result;
};