较大的字符数组读写问题

[lxingbo]

我想写一个小程序可以将A文件中所有AT字母互换, CG字母互换, 然后逆序输出到B文件中. 以下是我写的代码:

#include <stdio.h>
#include <malloc.h>
void main()
{
char ch,temp;
FILE *fp1, *fp2;
long n=0,i=0;
fp1=fopen("A.txt","r");
fp2=fopen("B.txt","w");
while(fgetc(fp1)!=EOF) //统计A文件中字符数
{n++;}
char *str=(char *)malloc(n*sizeof(ch)); //给str分配足够的内存空间
str="";
rewind(fp1);
while((ch=fgetc(fp1))!=EOF) //进行AT,CG互换
{if(ch=='A') str[i]='T';
if(ch=='T') str[i]='A';
if(ch=='C') str[i]='G';
if(ch=='G') str[i]='C';
i++;
}
str[i]='\0';
for(i=n-1;i>=0;i--) 将str逆序写入B文件中
{fputc(str[i],fp2);
}
free(str);
fclose(fp1);
fclose(fp2);
}

代码在turbo C++ 3.0中编译通过, 但是执行后, B文件中出现乱码. 想不明白是哪里的问题. 请高手指教.

[relaxisland]

单双引号的问题吧
字符是单引号。

[rainharder]

能编译过？

[ningzhiyu]

1。
str=""; //这里把指针指向了一个字符串常量，指针再不指向申请的动态内存，有大问题……如果是想清零，用memset

2。
//只在str中保存了几个要转换的数据，其他都没有保存下来
while((ch=fgetc(fp1))!=EOF) //进行AT,CG互换
{if(ch== "A ") str[i]= "T ";
if(ch== "T ") str[i]= "A ";
if(ch== "C ") str[i]= "G ";
if(ch== "G ") str[i]= "C ";
i++;
}

[cceczjxy]

char *str=(char *)malloc(n*sizeof(ch)); //给str分配足够的内存空间
str="";
...........................
free(str);

这样写,程序没崩溃是你幸运.str又被你指向了一个字符串常量了,free字符串常量是会报内存溢出的错误的.
-------------------------

[yydrewdrew]

改了一下，vs2005可以：
#include <stdio.h>
#include <malloc.h>
#include <string.h>
void main()
{
char ch,temp;
FILE *fp1,*fp2;
long n=0,i=0;
fp1 = fopen("C:\\Documents and Settings\\Rui.2B9F317BD5854FF\\桌面\\example\\A.txt","r");
fp2 = fopen("C:\\Documents and Settings\\Rui.2B9F317BD5854FF\\桌面\\example\\B.txt","w");
if(!fp1 || !fp2)
{
return;
}
while(fgetc(fp1) != EOF) //统计A文件中字符数
{
n++;
}
char *str=(char *)malloc((n * sizeof(ch)) + 1); //给str分配足够的内存空间
strcpy(str,"");
rewind(fp1);
while((ch = fgetc(fp1)) != EOF) //进行AT,CG互换
{
str[i] = ch;
if(ch == 'A') str[i] = 'T';
if(ch == 'T') str[i] = 'A';
if(ch == 'C') str[i] = 'G';
if(ch == 'G') str[i] = 'C';
i++;
}
str[i]= '\0';
for(i = n - 1;i != -1;i--) //将str逆序写入B文件中
{
fputc(str[i],fp2);
}
free(str);
fclose(fp1);
fclose(fp2);
}

[yydrewdrew]

尝试贴c++代码：）

#include <stdio.h>
#include <malloc.h>
#include <string.h>
void main()
{
char ch,temp;
FILE *fp1,*fp2;
long n=0,i=0;
fp1 = fopen("C:\\Documents and Settings\\Rui.2B9F317BD5854FF\\桌面\\example\\A.txt","r");
fp2 = fopen("C:\\Documents and Settings\\Rui.2B9F317BD5854FF\\桌面\\example\\B.txt","w");
if(!fp1 || !fp2)
{
return;
}
while(fgetc(fp1) != EOF) //统计A文件中字符数
{
n++;
}
char *str=(char *)malloc((n * sizeof(ch)) + 1); //给str分配足够的内存空间
strcpy(str,"");
rewind(fp1);
while((ch = fgetc(fp1)) != EOF) //进行AT,CG互换
{
str[i] = ch;
if(ch == 'A') str[i] = 'T';
if(ch == 'T') str[i] = 'A';
if(ch == 'C') str[i] = 'G';
if(ch == 'G') str[i] = 'C';
i++;
}
str[i]= '\0';
for(i = n - 1;i != -1;i--) //将str逆序写入B文件中
{
fputc(str[i],fp2);
}
free(str);
fclose(fp1);
fclose(fp2);
}

[yydrewdrew]

#include <stdio.h>
#include <malloc.h>
#include <string.h>
void main()
{
char ch,temp;
FILE *fp1,*fp2;
long n=0,i=0;
fp1 = fopen("C:\\Documents and Settings\\Rui.2B9F317BD5854FF\\桌面\\example\\A.txt","r");
fp2 = fopen("C:\\Documents and Settings\\Rui.2B9F317BD5854FF\\桌面\\example\\B.txt","w");
if(!fp1 || !fp2)
{
return;
}
while(fgetc(fp1) != EOF) //统计A文件中字符数
{
n++;
}
char *str=(char *)malloc((n * sizeof(ch)) + 1); //给str分配足够的内存空间
strcpy(str,"");
rewind(fp1);
while((ch = fgetc(fp1)) != EOF) //进行AT,CG互换
{
str[i] = ch;
if(ch == 'A') str[i] = 'T';
if(ch == 'T') str[i] = 'A';
if(ch == 'C') str[i] = 'G';
if(ch == 'G') str[i] = 'C';
i++;
}
str[i]= '\0';
for(i = n - 1;i != -1;i--) //将str逆序写入B文件中
{
fputc(str[i],fp2);
}
free(str);
fclose(fp1);
fclose(fp2);
}

[yydrewdrew]

#include   <stdio.h> 
#include   <malloc.h> 
#include  <string.h>
void   main() 
{ 
	char   ch,temp; 
	FILE   *fp1,*fp2; 
	long   n=0,i=0; 
	fp1 = fopen("C:\\Documents and Settings\\Rui.2B9F317BD5854FF\\桌面\\example\\A.txt","r"); 
	fp2 = fopen("C:\\Documents and Settings\\Rui.2B9F317BD5854FF\\桌面\\example\\B.txt","w"); 
	if(!fp1 || !fp2)
	{
		return;
	}
	while(fgetc(fp1) != EOF)   //统计A文件中字符数 
	{
		n++;
	}
	char *str=(char *)malloc((n * sizeof(ch)) + 1);   //给str分配足够的内存空间 
	strcpy(str,""); 
	rewind(fp1); 
	while((ch = fgetc(fp1)) != EOF)     //进行AT,CG互换 
	{
		str[i] = ch;
		if(ch == 'A')   str[i] = 'T'; 
		if(ch == 'T')   str[i] = 'A'; 
		if(ch == 'C')   str[i] = 'G'; 
		if(ch == 'G')   str[i] = 'C'; 
		i++; 
	}
	str[i]= '\0';
	for(i = n - 1;i != -1;i--) //将str逆序写入B文件中 
	{
		fputc(str[i],fp2); 
	} 
	free(str); 
	fclose(fp1); 
	fclose(fp2); 
} 

[laiwusheng]

楼上都回答了，我就来蹭点分吧

[laiwusheng]

楼主该不会是学生物的吧

[luvi88]

8楼做得不错。

[Hunter8212]

这么多分啊
来蹭点儿分……

[shu_yoyo]

８楼不错～～～