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Question:
How to use Atoi function and convert string to an actual integer using C++

Summary

Suppose:

Function: atoi 

String: s


Solution

//User function template for C++


class Solution{

  public:

    /*You are required to complete this method */

    int atoi(string s) {

        int n=s.size();

        int start=0;

        int sign=1;

        int ans=0;

        

        if(s[0]=='-'){

            sign=-1;

            start++;

        }

        

        for(int i=start; i<n; i++){

            if(s[i]>=48 && s[i]<=57){

                ans=(ans*10) + (s[i]-48);

            }

            else return -1;

        }

        

        return ans*sign;

    }

};


Explanation

  • Variables like start, sign, and ans are initialized in order to track the starting index, determine whether the number is negative, and accumulate the numerical value.

  • The beginning index is increased and the sign is set to -1 if the string begins with a negative sign.

  • The function then goes through the string's characters one by one.


Answered by:> >gore2612patil

Credit:> >GeekforGeeks


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