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 digits.
Example 1:
Input: s = "42"
Output: 42
Explanation: The underlined characters are what is read in, the caret is the current reader position.
Step 1: "42" (no characters read because there is no leading whitespace)
^
Step 2: "42" (no characters read because there is neither a '-' nor '+')
^
Step 3: "42" ("42" is read in)
^
The parsed integer is 42.
Since 42 is in the range [-231, 231 - 1], the final result is 42.
Given a signed 32-bit integer x, return x with its digits reversed. If reversing x causes the value to go outside the signed 32-bit integer range [-231, 231 - 1], then return 0.
Assume the environment does not allow you to store 64-bit integers (signed or unsigned).
Example 1:
Input: x = 123
Output: 321
Example 2:
Input: x = -123
Output: -321
Example 3:
Input: x = 120
Output: 21
Constraints:
-231 <= x <= 231 - 1
解題方向：
1. 這題是要反轉數字後保留正負數符號
2. 先轉成字串, 在檢查第一個文字是不是 '-1' 是的話就記錄負數
3. 再反轉紀錄文字, 最後再轉成數字和疊加正負數符號
4. 結果沒落在 -231 <= x <= 231 - 1 就要回傳 0
程式碼 ：
/** * @param {number} x * @return {number} */var reverse = function(x) {
const stringX = x.toString();
let index = 0;
let revertStringX = '';
let isPositive = true;
while (index < stringX.length) {
const letter = stringX[index];
if (index === 0 && letter === '-') {
isPositive = false;
} else {
revertStringX = letter + revertStringX;
}
index++;
}
let result = 0;
if (isPositive) {
result = parseInt(revertStringX);
} else {
result = -(parseInt(revertStringX));
}
if (result < -2147483648 || result > 2147483649) { return0;}
return result;
};
The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)
