输入十六进制，输出十进制

#include "stdafx.h"
#include <stdio.h>
#include "iostream"

int covert(char str[])
{
	int i;
	int sum = 0;
	for(i = 0; str[i]!='\0';i++)
	{
		if(str[i]>='0' && str[i] <='9')
			sum = sum*16+str[i]-'0';
		if(str[i]>='a' && str[i] <='f')
			sum = sum*16+str[i]-'a'+10;
		if(str[i]>='A' && str[i] <='F')
			sum = sum*16+str[i]-'A'+10;
		
	}
	return sum;
}
int main ()
{
	char str[1000];
	int i=0,c;
	printf("please input 16进制：");

	int flag1 = 1;//写入开关
	int flag = 0;//转换开关

	while((c=getchar())!='\0'&& flag1 )//判断并写入字符串
	{	
		if(c>='0' && c<='9' || c>='a' && c<='f' || c>='A' && c<='F' )
			{	
				
				flag = 1;//待转换
				str[i++] = c;//写入
			}
	
		else if(flag)//转换开关
		{
			str[i] = '\0';//字符串结束赋值
			printf("decimal number is : %d\n", covert(str));
			printf("Continue or stop?");
			c = getchar();
			if (c == 'N'|| c == 'n')
				flag1 = 0;//不进入等待赋值状态
			else
			{
				flag = 0;//等待赋值
				i = 0; //下标归零
				printf("Continue,please input 16进制:");
			}
		}

	}
		
	system("pause");
	return 0;
}