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8. String to Integer atoi.go
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8. String to Integer atoi.go
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package leetcode
func myAtoi(s string) int {
maxInt, signAllowed, whitespaceAllowed, sign, digits := int64(2<<30), true, true, 1, []int{}
for _, c := range s {
if c == ' ' && whitespaceAllowed {
continue
}
if signAllowed {
if c == '+' {
signAllowed = false
whitespaceAllowed = false
continue
} else if c == '-' {
sign = -1
signAllowed = false
whitespaceAllowed = false
continue
}
}
if c < '0' || c > '9' {
break
}
whitespaceAllowed, signAllowed = false, false
digits = append(digits, int(c-48))
}
var num, place int64
place, num = 1, 0
lastLeading0Index := -1
for i, d := range digits {
if d == 0 {
lastLeading0Index = i
} else {
break
}
}
if lastLeading0Index > -1 {
digits = digits[lastLeading0Index+1:]
}
var rtnMax int64
if sign > 0 {
rtnMax = maxInt - 1
} else {
rtnMax = maxInt
}
digitsCount := len(digits)
for i := digitsCount - 1; i >= 0; i-- {
num += int64(digits[i]) * place
place *= 10
if digitsCount-i > 10 || num > rtnMax {
return int(int64(sign) * rtnMax)
}
}
num *= int64(sign)
return int(num)
}