LeetCode #8

# Description:

Implement atoi to convert a string to an integer.

Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input cases.

Notes: It is intended for this problem to be specified vaguely (ie, no given input specs). You are responsible to gather all the input requirements up front.

## Example:

``````Note
``````

# Idea:

2. 正负号
3. 不是数的别的symbol
4. overflow

# Code:

``````class Solution {
public:
int myAtoi(string str) {
int sign=1;
int maxDiv10=INT_MAX/10;

int i=0;
while(i<str.size()&&str[i]==' ')  // Take care of the leading spaces
i++;

if(i==str.size()) return 0;

if(str[i]=='+'){ // Take care of the sign
i++;
}
else if(str[i]=='-'){
i++;
sign=-1;
}
int num=0;
while(i<str.size()&&isdigit(str[i])){
int digit=str[i]-'0';
if(num>maxDiv10 || (num==maxDiv10&&digit>=8) ) // Take care of the overflow case
return sign==1? INT_MAX: INT_MIN;

num = num*10 + digit;
i++;
}
return sign*num;
}
};
``````