3.cpp

判断输入的数字串是否为偶数

//判断输入的数字串是否为偶数，用mod 2完成
#include <stdio.h>
#include <conio.h>
#include <stdlib.h>
#define BASELEN 10
#define INCRENTMENT 10

void main()
{
	char *p;
	FILE *fp;
	long Num=0;
	int i=0;
	int CurLen=0;
	int MaxLen=BASELEN;
	clrscr();
	if (!(fp=fopen("c:\\2.txt","r")))
	{
		printf ("Open file error.\n");
		exit(0);
	}
	if (!(p=(char*)malloc(sizeof(char)*BASELEN)))
	{
		printf ("Malloc Error.\n");
	}
	while(1)
	{
		if (CurLen==MaxLen)
		{
			MaxLen=MaxLen+INCRENTMENT;
			if (!(p=(char *)realloc(p,sizeof(char)*MaxLen)))
			{
				printf ("Realloc error.\n");
			}
		}
		fscanf(fp,"%c",p+i);
		if (*(p+i)=='\n') break;
		CurLen++;i++;
	}
	i=0;
		for(;(*(p+i)>='0') && (*(p+i)<='9');i++)
		{
			Num=Num*10+(*(p+i)-'0');
		}

	if (*(p+i)=='\n' && i!=0)
		if (Num%2==0)
			printf ("TRUE.\n");
		else
			printf ("FALSE.\n");
	else
		printf ("ERROR.\n");
 fclose(fp);
}