scanf和gets函数的区别解决办法
scanf和gets函数的区别
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define PI 3.14159
int main()
{
int x,y,z;
char reciv[11];
while(1)
{
double dist,gallo_need;
gets(reciv);
if(strcmp(reciv,"ENDOFINPUT")==0)
break;
scanf("%d %d %d",&x,&y,&z);//连续输入会在缓存区留下\n
fflush(stdin);
gets(reciv);//
dist=2*PI*x*z/360;
gallo_need=2*dist/5;
if(gallo_need>y)
{
printf("NO %d\n",y*5);
}
else
printf("YES %d\n",(int)(y-gallo_need));
}
return 0;
}
从这段代码，我发现gets这个函数实际上不会将\n放进缓冲区，scanf才会，网上说法不一
有的说gets会，有的说不会
但是如果我把里面的gets全改为scanf
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define pi 3.14159
int main()
{
while(1)
{
double dist,fuel_need;
char reciv[12];
int x,y,z;
scanf("%s",reciv);
if(strcmp(reciv,"ENDOFINPUT")==0)
{
break;
}
scanf("%d %d %d",&x,&y,&z);
scanf("%s",reciv);
if(z>180)
z=360-z;
dist=2*pi*x*z/360;
fuel_need=2*dist/5;
if(fuel_need>y)
{
printf("NO %d",y*5);
}
else
printf("YES %d",(int)(y-fuel_need));
}
return 0;
}
那么十七行和十八行以及下一次进入while循环，上一次循环的十八行和这次的12行怎么不会出问题呢？按上一段代码，scanf是会将\n放进缓冲区的啊？
------解决思路----------------------
Format Specification Fields: scanf and wscanf Functions
A format specification has the following form:
%[*] [width] [{h
------解决思路----------------------
l
------解决思路----------------------
I64
------解决思路----------------------
L}]type
The format argument specifies the interpretation of the input and can contain one or more of the following:
White-space characters: blank (' '); tab ('\t'); or newline ('\n'). A white-space character causes scanf to read, but not store, all consecutive white-space characters in the input up to the next non–white-space character. One white-space character in the format matches any number (including 0) and combination of white-space characters in the input.
Non–white-space characters, except for the percent sign (%). A non–white-space character causes scanf to read, but not store, a matching non–white-space character. If the next character in stdin does not match, scanf terminates.
Format specifications, introduced by the percent sign (%). A format specification causes scanf to read and convert characters in the input into values of a specified type. The value is assigned to an argument in the argument list.
The format is read from left to right. Characters outside format specifications are expected to match the sequence of characters in stdin; the matching characters in stdin are scanned but not stored. If a character in stdin conflicts with the format specification, scanf terminates, and the character is left in stdin as if it had not been read.
When the first format specification is encountered, the value of the first input field is converted according to this specification and stored in the location that is specified by the first argument. The second format specification causes the second input field to be converted and stored in the second argument, and so on through the end of the format string.
An input field is defined as all characters up to the first white-space character (space, tab, or newline), or up to the first character that cannot be converted according to the format specification, or until the field width (if specified) is reached. If there are too many arguments for the given specifications, the extra arguments are evaluated but ignored. The results are unpredictable if there are not enough arguments for the format specification.
Each field of the format specification is a single character or a number signifying a particular format option. The type character, which appears after the last optional format field, determines whether the input field is interpreted as a character, a string, or a number.
The simplest format specification contains only the percent sign and a type character (for example, %s). If a percent sign (%) is followed by a character that has no meaning as a format-control character, that character and the following characters (up to the next percent sign) are treated as an ordinary sequence of characters, that is, a sequence of characters that must match the input. For example, to specify that a percent-sign character is to be input, use %%.
An asterisk (*) following the percent sign suppresses assignment of the next input field, which is interpreted as a field of the specified type. The field is scanned but not stored.
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define PI 3.14159
int main()
{
int x,y,z;
char reciv[11];
while(1)
{
double dist,gallo_need;
gets(reciv);
if(strcmp(reciv,"ENDOFINPUT")==0)
break;
scanf("%d %d %d",&x,&y,&z);//连续输入会在缓存区留下\n
fflush(stdin);
gets(reciv);//
dist=2*PI*x*z/360;
gallo_need=2*dist/5;
if(gallo_need>y)
{
printf("NO %d\n",y*5);
}
else
printf("YES %d\n",(int)(y-gallo_need));
}
return 0;
}
从这段代码，我发现gets这个函数实际上不会将\n放进缓冲区，scanf才会，网上说法不一
有的说gets会，有的说不会
但是如果我把里面的gets全改为scanf
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define pi 3.14159
int main()
{
while(1)
{
double dist,fuel_need;
char reciv[12];
int x,y,z;
scanf("%s",reciv);
if(strcmp(reciv,"ENDOFINPUT")==0)
{
break;
}
scanf("%d %d %d",&x,&y,&z);
scanf("%s",reciv);
if(z>180)
z=360-z;
dist=2*pi*x*z/360;
fuel_need=2*dist/5;
if(fuel_need>y)
{
printf("NO %d",y*5);
}
else
printf("YES %d",(int)(y-fuel_need));
}
return 0;
}
那么十七行和十八行以及下一次进入while循环，上一次循环的十八行和这次的12行怎么不会出问题呢？按上一段代码，scanf是会将\n放进缓冲区的啊？
------解决思路----------------------
Format Specification Fields: scanf and wscanf Functions
A format specification has the following form:
%[*] [width] [{h
------解决思路----------------------
l
------解决思路----------------------
I64
------解决思路----------------------
L}]type
The format argument specifies the interpretation of the input and can contain one or more of the following:
White-space characters: blank (' '); tab ('\t'); or newline ('\n'). A white-space character causes scanf to read, but not store, all consecutive white-space characters in the input up to the next non–white-space character. One white-space character in the format matches any number (including 0) and combination of white-space characters in the input.
Non–white-space characters, except for the percent sign (%). A non–white-space character causes scanf to read, but not store, a matching non–white-space character. If the next character in stdin does not match, scanf terminates.
Format specifications, introduced by the percent sign (%). A format specification causes scanf to read and convert characters in the input into values of a specified type. The value is assigned to an argument in the argument list.
The format is read from left to right. Characters outside format specifications are expected to match the sequence of characters in stdin; the matching characters in stdin are scanned but not stored. If a character in stdin conflicts with the format specification, scanf terminates, and the character is left in stdin as if it had not been read.
When the first format specification is encountered, the value of the first input field is converted according to this specification and stored in the location that is specified by the first argument. The second format specification causes the second input field to be converted and stored in the second argument, and so on through the end of the format string.
An input field is defined as all characters up to the first white-space character (space, tab, or newline), or up to the first character that cannot be converted according to the format specification, or until the field width (if specified) is reached. If there are too many arguments for the given specifications, the extra arguments are evaluated but ignored. The results are unpredictable if there are not enough arguments for the format specification.
Each field of the format specification is a single character or a number signifying a particular format option. The type character, which appears after the last optional format field, determines whether the input field is interpreted as a character, a string, or a number.
The simplest format specification contains only the percent sign and a type character (for example, %s). If a percent sign (%) is followed by a character that has no meaning as a format-control character, that character and the following characters (up to the next percent sign) are treated as an ordinary sequence of characters, that is, a sequence of characters that must match the input. For example, to specify that a percent-sign character is to be input, use %%.
An asterisk (*) following the percent sign suppresses assignment of the next input field, which is interpreted as a field of the specified type. The field is scanned but not stored.