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 charcter 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
`[-2`

, then clamp the integer so that it remains in the range. Specifically, integers less than^{31}, 2^{31}- 1]`-2`

should be clamped to^{31}`-2`

, and integers greater than^{31}`2`

should be clamped to^{31}- 1`2`

.^{31}- 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:42Explanation: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 [-2^{31}, 2^{31}- 1], the final result is 42.

**Example 2:**

Input:s = " -42"Output:-42Explanation:Step 1: "-42" (leading whitespace is read and ignored) ^ Step 2: "-42" ('-' is read, so the result should be negative) ^ Step 3: " -42" ("42" is read in) ^ The parsed integer is -42. Since -42 is in the range [-2^{31}, 2^{31}- 1], the final result is -42.

**Example 3:**

Input:s = "4193 with words"Output:4193Explanation:Step 1: "4193 with words" (no characters read because there is no leading whitespace) ^ Step 2: "4193 with words" (no characters read because there is neither a '-' nor '+') ^ Step 3: "4193with words" ("4193" is read in; reading stops because the next character is a non-digit) ^ The parsed integer is 4193. Since 4193 is in the range [-2^{31}, 2^{31}- 1], the final result is 4193.

**Example 4:**

Input:s = "words and 987"Output:0Explanation:Step 1: "words and 987" (no characters read because there is no leading whitespace) ^ Step 2: "words and 987" (no characters read because there is neither a '-' nor '+') ^ Step 3: "words and 987" (reading stops immediately because there is a non-digit 'w') ^ The parsed integer is 0 because no digits were read. Since 0 is in the range [-2^{31}, 2^{31}- 1], the final result is 0.

**Example 5:**

Input:s = "-91283472332"Output:-2147483648Explanation:Step 1: "-91283472332" (no characters read because there is no leading whitespace) ^ Step 2: "-91283472332" ('-' is read, so the result should be negative) ^ Step 3: "-91283472332" ("91283472332" is read in) ^ The parsed integer is -91283472332. Since -91283472332 is less than the lower bound of the range [-2^{31}, 2^{31}- 1], the final result is clamped to -2^{31}= -2147483648.

**Constraints:**

`0 <= s.length <= 200`

`s`

consists of English letters (lower-case and upper-case), digits (`0-9`

),`' '`

,`'+'`

,`'-'`

, and`'.'`

.

public int MyAtoi(string s) {
s = s.Trim();
StringBuilder numberBuilder = new StringBuilder();
bool isNegative = false;
bool foundNumber = false;
for (int i = 0; i < s.Length; i++)
{
char c = s[i];
if ((c == '-' || c == '+') && i + 1 < s.Length && char.IsNumber(s[i + 1]) && !isNegative && !foundNumber)
{
if(c=='-')
{
isNegative = true;
}
continue;
}
if(!foundNumber)
{
if(!char.IsNumber(s[i])){
break;
}
if (s[i] != 0)
{
numberBuilder.Append(s[i]);
}
foundNumber = true;
continue;
}
if (char.IsNumber(s[i]))
{
numberBuilder.Append(s[i]);
continue;
}
break;
}
if (!foundNumber) return 0;
try
{
int number = isNegative ? int.Parse(numberBuilder.ToString()) * -1 : int.Parse(numberBuilder.ToString());
return number;
}
catch (OverflowException e)
{
return isNegative ? int.MinValue : int.MaxValue;
}
}

The basic idea is to understand the question thoroughly, then cover all the edge cases. A detailed explanation is provided in the video.

Time Complexity: O(n) // where n is the length of string

Space Complexity: O(1) // we don't require any extra space.