String to Integer (atoi) LeetCode Solution

Problem: https://leetcode.com/problems/string-to-integer-atoi/

Solution in C++

#

class Solution { public: int myAtoi(string s) { int i, n = s.length();

    if(n == 0){
        return 0;
    }
    
    long long int ans = 0;
    
    int sign = 1;
    bool flag = false;
    
    for(i=0;i<n;i++)
    {
        if(!isValid(s\[i\])){
            return ans;
        }
        
        else if(s\[i\] == ' ')
        {
            // haven't encountered a sign character yet
            if(flag == false)
                continue;
            else
                return ans;
        }
        
        else if(s\[i\]=='-')
        {
            if(flag == false)
            {
                sign = -1;
                flag = true;
            }
            else
                return ans;
        }
        
        else if(s\[i\]=='+')
        {
            if(flag == false)
                flag = true;
            else
                return ans;
        }
        
        else
        {
            ans = abs(ans) \* 10 + (s\[i\] - '0');
            ans = ans\*sign;
            if(ans >= INT\_MAX)
                return INT\_MAX;
            else if(ans <= INT\_MIN)
                return INT\_MIN;
            flag = true;
        }
    }
     return ans;
}

bool isValid(char c)
{
    if(c=='0' || c=='1' || c=='2' || c=='3' || c=='4' || c=='5'|| c=='6' 
       || c=='7' || c=='8' || c=='9' || c==' ' || c=='-' || c=='+')
        return true;
    return false;
}

};