String to Integer (atoi), Medium
Implement the myAtoi(string s) function, which converts a string to a 32-bit signed integer.
The algorithm for myAtoi(string s) is as follows:
Whitespace: Ignore any leading whitespace (" ").
Signedness: Determine the sign by checking if the next character is '-' or '+', assuming positivity if neither present.
Conversion: Read the integer by skipping leading zeros until a non-digit character is encountered or the end of the string is reached. If no digits were read, then the result is 0.
Rounding: If the integer is out of the 32-bit signed integer range [-231, 231 - 1], then round the integer to remain in the range. Specifically, integers less than -231 should be rounded to -231, and integers greater than 231 - 1 should be rounded to 231 - 1.
Return the integer as the final result.
Solution, Typescript
function myAtoi(s: string): number {s = s.trim(); // remove whitespacelet sign = 1;let startIdx = 0;let endIdx = s.length - 1;// detect signedneessif(s.charAt(0) === "-") {sign = -1;startIdx++;} else if(s.charAt(0) === "+") {startIdx++;}// skip leading zeroswhile(true) {if(s.charAt(startIdx) !== "0") {break}startIdx++;}let val = 0;let placeVal = 1;for(let i = endIdx; i >= startIdx; i--) {let digit = digitConvert(s.charAt(i));if(digit == -1) {val = 0;placeVal = 1;continue;}val += digit * placeVal;placeVal *= 10;}val = sign*val;// console.log(val)val = Math.max(val, -(2**31));// console.log(val, (-2)**31)val = Math.min(val, 2**31 - 1);// console.log(val, 2**31 - 1)return val;};function digitConvert(s: string): number {switch(s) {case "0":return 0;case "1":return 1;case "2":return 2;case "3":return 3;case "4":return 4;case "5":return 5;case "6":return 6;case "7":return 7;case "8":return 8;case "9":return 9;default:return -1;}