8. String to Integer atoi.go

package leetcode

funcmyAtoi(sstring) int {
maxInt, signAllowed, whitespaceAllowed, sign, digits:=int64(2<<30), true, true, 1, []int{}
for_, c:=ranges {
ifc==' '&&whitespaceAllowed {
continue
 }
ifsignAllowed {
ifc=='+' {
signAllowed=false
whitespaceAllowed=false
continue
 } elseifc=='-' {
sign=-1
signAllowed=false
whitespaceAllowed=false
continue
 }
 }
ifc<'0'||c>'9' {
break
 }
whitespaceAllowed, signAllowed=false, false
digits=append(digits, int(c-48))
 }
varnum, placeint64
place, num=1, 0
lastLeading0Index:=-1
fori, d:=rangedigits {
ifd==0 {
lastLeading0Index=i
 } else {
break
 }
 }
iflastLeading0Index>-1 {
digits=digits[lastLeading0Index+1:]
 }
varrtnMaxint64
ifsign>0 {
rtnMax=maxInt-1
 } else {
rtnMax=maxInt
 }
digitsCount:=len(digits)
fori:=digitsCount-1; i>=0; i-- {
num+=int64(digits[i]) *place
place*=10
ifdigitsCount-i>10||num>rtnMax {
returnint(int64(sign) *rtnMax)
 }
 }
num*=int64(sign)
returnint(num)
}