[C++]Leetcode #8 atoi()

class Solution {public:    int myAtoi(string str) {        int n=str.length();        int number[n];        int j=-1, flag=0;        for(int i=0;i<n;i++)        {        if(str[i]=='+' || str[i]=='-')        {        if(isdigit(str[i+1])==false)        {        return 0;        }        }            if(isdigit(str[i])==true)            {            j=j+1;                number[j]=int(str[i]-'0');                if(i>=1)                {                   if(str[i-1]=='+')                {                    flag=0;                }                else if(str[i-1]=='-')                {                    flag=1;                }                                else if(str[i-1]!=' '&&isdigit(str[i-1])==false){                   return 0 ;                }                                                      }if(i>=2){if((str[i-1]=='+')&&(str[i-2]=='-')){return 0;}if((str[i-1]=='-')&&(str[i-2]=='+')){return 0;}}                if(i+1<n){                if(isdigit(str[i+1])==false)                {                    break;                }                }            }        }        long long result=0;        for(int k=j;k>=0;k--)        {            unsigned long x=number[k]*pow(10,j-k);                        if(flag==0){                result=result+x;            }            else{                result=result-x;            }        if(result>=INT_MAX)        {            return INT_MAX;        }        if(result<=INT_MIN)        {            return INT_MIN;        }                                           }               return result;    }};