Thread: Atoi()

Hello.

I am trying to implement atoi(). Below is my code. It compiles correctly, but output is not correct. can anyone correct what wrong i am doing in logic here.
Here is my code.

Code:

#include<iostream>
#include<string>
#include<cmath>
using namespace std;

int myAtoi(const char*);

int main(){
    char abc[] = {"234"};
    int c = myAtoi(abc);
    cout<<c;
    system("PAUSE");
    }
    
int myAtoi(const char* str){
    if(str == NULL){
           cout<<"String is empty";
           return 0;
           }
    int sum = 0, j, len;
    len = strlen(str);
    j = len-1;
    while(j>=0){
                sum = sum + (((int)str[j]) * (pow(10.0,j)));
                j--;
                }
    return sum;
}

Thanks.

Thanks.

I modified code as below, but still answer is not correct.

Code:

#include<iostream>
#include<string>
#include<cmath>
using namespace std;

int myAtoi(const char*);

int main(){
    char abc[] = {"234"};
    cout<<strlen(abc)<<endl;
    int c = myAtoi(abc);
    cout<<c;
    system("PAUSE");
    }
    
int myAtoi(const char* str){
    if(str == NULL){
           cout<<"String is empty";
           return 0;
           }
    int sum = 0, j, len, k = 0;
    len = strlen(str);
    j = len-1;
    while(j>=0){
                sum = sum + ((str[j] - 30) * (pow(10.0,j)));
                j--;
                }
    return sum;
}

I meant the hexademical 0x30 to 0x39, sorry (subtract 0x30 or 48).

Also your powers are incorrect, as you get further down the string, the exponent should decrease (the number to the farmost right is the least significant so should get a power of 0, use len-j-1).