P176. Implement user defined ( atoi ) function.

 

#include<stdio.h>

#include<stdlib.h>

int my_atoi(const char *);

void main(int argc,char **argv)

{

        int flag,i;

        if(argc<2)

                printf("Usage: a.out String \n");

 

        int num = my_atoi(argv[1]);

        printf("%d\n",num);

}

 

int my_atoi(const char *p)

{

    int i,num;

    if(p[0]=='-'|| p[0]=='+')

        i=1;

 

    else

        i=0;

 

    for(num=0;p[i];i++)

    {

        if(p[i]>'0' && p[i]<'9')

        num=num*10+(p[i]-48);

 

        else

        break;

 

    }

        if(p[0]=='-')

        num=-num;

 

        return num;

}