class Solution {
public:
    int myAtoi(string s) {
        if(s.empty()) return 0;
        
        const long long MAX_INT = INT_MAX;
        const long long MIN_INT = INT_MIN;

        int n = s.length();
        int i = 0;
        while(i<n && s[i]==' ')
            i++;
        if(i==n)
            return 0;    
        int sign = 1;
        if(s[i]=='+')
            i++;
        else if(s[i]== '-'){
            sign = -1;
            i++;
        }

        long long res= 0;
        while(i<n && isdigit(s[i])){
            int digit = s[i] - '0';
            res = res*10 + digit;

            if(sign*res >= MAX_INT)
                return MAX_INT;
            if(sign*res <= MIN_INT)
                return MIN_INT;
            i++;        
        }  
        return sign*res;     
    }

};