/
8
151 lines (139 loc) · 3.86 KB
/
8
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//版本一:
int myAtoi(string str) {
if(str.size()==0)
return 0;
int i=0;
while(str[i]==' ')
i++;
bool minus=false;
long long num=0;
if(str[i]=='-')
{
minus=true;
i++;
if(str[i]<'0'||str[i]>'9')
return num;
}
if(str[i]=='+')
{
minus=false;
i++;
if(str[i]<'0'||str[i]>'9')
return num;
}
if(str[i]<'0'&&str[i]>'9')
return num;
while(str[i]!='\0'&&str[i]>='0'&&str[i]<='9')
{
num=num*10+(str[i]-'0');
//检查是否溢出
if(num==2147483649)
return -2147483648;
if(minus==true&&num>0xFFFFFFFF)
return -2147483648;
if(minus==true&&num<(signed int)0x800000000)
return -2147483648;
if(minus==false&&num>0x7FFFFFFF)
return (int)0x7FFFFFFF;
i++;
}
if(minus==false)
return num;
else
return 0-num;
}
//版本二:
bool isValidNum(char c){
if((c>='0'&&c<='9')||c=='-'||c=='+')
{
return true;
}
else
return false;
}
int char2num(char c){
return c-'0';
}
int myAtoi(string str) {
bool isMinus=false;
bool isStart = false;
int size = str.size();
int ans = 0;
if(size<=0)
{
return 0;
}
for(int i=0;i<size;i++)
{
if(!isValidNum(str[i])&&!isStart){
if(str[i]==' ')
continue;
else return 0;
}
else if(!isStart&&str[i]=='-'){
isMinus=true;
isStart = true;
}
else if(!isStart&&str[i]=='+'){
isMinus=false;
isStart = true;
}
else if(isValidNum(str[i]))
{
if(isStart&&str[i]=='-')
{
if(isMinus)
return -ans;
else
return ans;
}else if(isStart&&str[i]=='+')
{
if(isMinus)
return -ans;
else
return ans;
}
if(!isStart){
isStart=true;
ans*=10;
ans+=(str[i]-'0');
}else
{
if(ans<=214748364)
{
ans*=10;
}
else{
if(isMinus){
return INT_MIN;
}else{
return INT_MAX;
}
}
if(ans>=2147483640){
if(isMinus){
if((str[i]-'0')>=8)
return INT_MIN;
else{
return -(ans+(str[i]-'0'));
}
}else{
if((str[i]-'0')>=7)
return INT_MAX;
else
return ans+(str[i]-'0');
}
}
else
ans+=(str[i]-'0');
}
}
else if(isStart&&!isValidNum(str[i])){
break;
}
}
if(isMinus)
return -ans;
else
return ans;
}