leetcode-algorithms/src/StringToIntegerAtoi.java at master · anishLearnsToCode/leetcode-algorithms · GitHub

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// https://leetcode.com/problems/string-to-integer-atoi

// T:O(|input|)

// S:O(1)

public class StringToIntegerAtoi {

public int myAtoi(String input) {

int sign = 1;

int result = 0;

int index = 0;

int n = input.length();

// Discard all spaces from the beginning of the input string.

while (index < n && input.charAt(index) == ' ') {

index++;

}

// sign = +1, if it's positive number, otherwise sign = -1.

if (index < n && input.charAt(index) == '+') {

index++;

} else if (index < n && input.charAt(index) == '-') {

sign = -1;

index++;

}

// Traverse next digits of input and stop if it is not a digit

while (index < n && Character.isDigit(input.charAt(index))) {

int digit = input.charAt(index) - '0';

// Check overflow and underflow conditions.

if ((result > Integer.MAX_VALUE / 10) ||

(result == Integer.MAX_VALUE / 10 && digit > Integer.MAX_VALUE % 10)) {

// If integer overflowed return 2^31-1, otherwise if underflowed return -2^31.

return sign == 1 ? Integer.MAX_VALUE : Integer.MIN_VALUE;

}

// Append current digit to the result.

result = 10 * result + digit;

index++;

}

// We have formed a valid number without any overflow/underflow.

// Return it after multiplying it with its sign.

return sign * result;

}

leetcode-algorithms/src/StringToIntegerAtoi.java at master · anishLearnsToCode/leetcode-algorithms · GitHub

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