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72 lines
2.7 KiB
72 lines
2.7 KiB
2 years ago
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8. String to Integer (atoi)
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Medium
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Implement the myAtoi(string s) function, which converts a string to a 32-bit signed integer (similar to C/C++'s atoi function).
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The algorithm for myAtoi(string s) is as follows:
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Read in and ignore any leading whitespace.
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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.
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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.
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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).
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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.
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Return the integer as the final result.
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Note:
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Only the space character ' ' is considered a whitespace character.
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Do not ignore any characters other than the leading whitespace or the rest of the string after the digits.
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Example 1:
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Input: s = "42"
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Output: 42
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Explanation: The underlined characters are what is read in, the caret is the current reader position.
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Step 1: "42" (no characters read because there is no leading whitespace)
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^
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Step 2: "42" (no characters read because there is neither a '-' nor '+')
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^
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Step 3: "42" ("42" is read in)
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^
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The parsed integer is 42.
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Since 42 is in the range [-231, 231 - 1], the final result is 42.
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Example 2:
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Input: s = " -42"
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Output: -42
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Explanation:
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Step 1: " -42" (leading whitespace is read and ignored)
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^
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Step 2: " -42" ('-' is read, so the result should be negative)
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^
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Step 3: " -42" ("42" is read in)
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^
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The parsed integer is -42.
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Since -42 is in the range [-231, 231 - 1], the final result is -42.
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Example 3:
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Input: s = "4193 with words"
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Output: 4193
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Explanation:
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Step 1: "4193 with words" (no characters read because there is no leading whitespace)
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^
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Step 2: "4193 with words" (no characters read because there is neither a '-' nor '+')
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^
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Step 3: "4193 with words" ("4193" is read in; reading stops because the next character is a non-digit)
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^
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The parsed integer is 4193.
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Since 4193 is in the range [-231, 231 - 1], the final result is 4193.
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Constraints:
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0 <= s.length <= 200
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s consists of English letters (lower-case and upper-case), digits (0-9), ' ', '+', '-', and '.'.
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