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LeetCode 8: String to Integer (atoi) Solution

Master LeetCode problem 8 (String to Integer (atoi)), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

8. String to Integer (atoi)

Medium
String

Problem Explanation

Explanation:

To solve this problem, we need to follow the steps outlined in the problem description: ignoring leading whitespace, determining sign, converting the integer, and handling rounding. We can achieve this by iterating over the characters in the string and updating our result accordingly.

  1. Trim leading whitespace.
  2. Determine sign.
  3. Convert the integer value.
  4. Handle rounding for out-of-range values.

Time Complexity: O(n) where n is the length of the input string. Space Complexity: O(1)

:

Solution Code

class Solution {
    public int myAtoi(String s) {
        if (s.isEmpty()) return 0;

        int i = 0, sign = 1, result = 0;
        while (i < s.length() && s.charAt(i) == ' ') {
            i++;
        }

        if (i < s.length() && (s.charAt(i) == '+' || s.charAt(i) == '-')) {
            sign = (s.charAt(i) == '-') ? -1 : 1;
            i++;
        }

        while (i < s.length() && Character.isDigit(s.charAt(i))) {
            int digit = s.charAt(i) - '0';

            if (result > Integer.MAX_VALUE / 10 || (result == Integer.MAX_VALUE / 10 && digit > Integer.MAX_VALUE % 10)) {
                return (sign == 1) ? Integer.MAX_VALUE : Integer.MIN_VALUE;
            }

            result = result * 10 + digit;
            i++;
        }

        return result * sign;
    }
}

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