经典案例--十六进制转换为十进制

1、方法一 用一级指针

#include <stdio.h>#include <string.h>#include <stdlib.h>int convert(char *myp, int mylen, int *Poutput)    {    int i = 0;    char *pstart = myp + 1;    char *Pstop = myp + mylen - 1;    int ant = 0;    int hex = 1;    if(Pstop == NULL )    {        return -1;    }    if(myp == NULL)        {        return -1;    }    while(Pstop > pstart)        {        for(i = 0; i < mylen - 2; i++)            {            if(*Pstop >= 'A' && *Pstop <= 'F')                {                ant = ant + (*Pstop - 'A' + 10) * hex;            }            else                {                ant = ant + (*Pstop - '0') * hex;                }                Pstop --;                hex = hex * 16;            }    }    *Poutput = ant;    return 0;}int main()    {    char buf1[10];    int  output = 0;    int len = 0;    int ret = 0;    scanf("%s",buf1);    len = strlen(buf1);    ret = convert(buf1,len,&output);    if(ret != 0)        {        printf("func convert() error!");        return ret;    }    printf("output:%d \n",output);    return 0;}

2、方法二 用二级指针

#include <stdio.h>#include <string.h>#include <stdlib.h>int convert(char *myp, int mylen, int **Poutput)    {    int i = 0;    char *pstart = myp + 1;    char *Pstop = myp + mylen - 1;    int ant = 0;    int hex = 1;    int *tmp = NULL;    tmp = (int *)malloc(10);    if(Pstop == NULL )    {        return -1;    }    if(myp == NULL)        {        return -1;    }    while(Pstop > pstart)        {        for(i = 0; i < mylen - 2; i++)            {            if(*Pstop >= 'A' && *Pstop <= 'F')                {                ant = ant + (*Pstop - 'A' + 10) * hex;            }            else                {                ant = ant + (*Pstop - '0') * hex;                }                Pstop --;                hex = hex * 16;            }    }    tmp = &ant;    *Poutput = tmp;    return 0;}int main()    {    char buf1[10];    int  *output = NULL;    int len = 0;    int ret = 0;    scanf("%s",buf1);    len = strlen(buf1);    ret = convert(buf1,len,&output);    if(ret != 0)        {        printf("func convert() error!");        return ret;    }    printf("output:%d \n",*output);    return 0;}