【answer】
Note that cross-border deal with simple problems like
there. .
Positive -2 ^ 31 can not take inverse number obtained from 2 ^ 31, since the positive int up to 2 ^ 31-1
[Code]
class Solution {
public:
bool isdigit(char key){
return (key>='0') && (key<='9');
}
int myAtoi(string str) {
int MAX_INT = (int)((1ll<<31)-1);
int MIN_INT = (int)(-(1ll<<31));
cout<<MAX_INT<<endl;
cout<<MIN_INT<<endl;
int len = str.size();
int idx = -1;
int f = 1;
for (int i = 0;i<len;i++){
if (str[i]!=' '){
if (str[i]=='-'){
f = -1;
idx = i+1;
}else if (str[i]=='+'){
idx = i+1;
}else if (isdigit(str[i])){
idx = i;
}
break;
}
}
if (idx==-1) return 0;
if (!isdigit(str[idx])) return 0;
int i = idx;
int temp = 0;
/*
2147483647
-2147483648
*/
while (i<len && isdigit(str[i])){
int x = str[i]-'0';
if (f==-1){
if (MIN_INT/10!=temp){
if (MIN_INT/10>temp)
return MIN_INT;
}else{
//MIN_INT/10==(-temp)
if (x>8){
return MIN_INT;
}
}
}else{
if (MAX_INT/10!=temp){
if (MAX_INT/10<temp){
return MAX_INT;
}
}else{
if (x>7) return MAX_INT;
}
}
//not exceed limitation
temp = temp*10+f*x;
i++;
}
return temp;
}
};