[英]How do I read numbers only from an array that has numbers and letters using C?
[英]How do I only accept numbers in C and block the user from entering letters and special characters?
我只需要弄清楚在用戶輸入的不是數字的情況下如何給出錯誤。 我已經設置了無法傳遞或無法通過的代碼值。
我只需要接受數字:如果輸入了字母或任何類型的特殊字符,我希望程序自行取消。 我怎樣才能做到這一點?
#include <stdio.h>
#include <math.h>
int main(void) {
float base, height;
float area;
printf("Please enter the value of base of the triangle: \n");
scanf ("%f", &base);
if(base<.5)
printf("Invalid Input\n");
while (base<.5)
return 0;
if(base>100)
printf("Invalid Input\n");
while(base>100)
return 0;
printf("Please enter the value of height of the triangle:\n");
scanf("%f", &height);
if(height<1)
printf("Invalid Input\n");
while(height<1)
return 0;
if(height>75)
printf("Invalid Input\n");
while (height>75)
return 0;
area = base * height/2;
printf("The area of the triangle for base: %f and height: %f is %f \n", base,
height , area );
return 0;
}
您不能阻止用戶輸入他或她想要的任何內容,但是可以使用scanf
的返回值來確定是否輸入了有效值,並提示用戶輸入正確的信息:
float base;
do {
printf("Please enter the value of base of the triangle: \n");
} while (scanf ("%f", &base) != 1 || base < .5 || base > 100);
該循環將繼續直到滿足所有三個條件:
scanf
返回了一項, scanf
提供的值大於或等於0.5
,並且 scanf
提供的值小於或等於100
scanf返回已成功匹配並填充值的變量數。 做就是了:
int result = scanf ("%f", &base);
if(result != 1)
{
...//handle error
}
我認為您可以逐字符讀取輸入的字符,然后檢查它是否為數字,如果不是,則顯示錯誤消息。
#include <stdio.h>
#include <math.h>
int main(void)
{
float base, height;
float area;
printf("Please enter the value of base of the triangle: \n");
char c='\n';
char success=0;
base=0;
char dot=0;
do{
scanf ("%c", &c);
if((c>=48)&&(c<=57)){
if(dot==0)
base=base*10+(c-48);
else{
base+=(c-48)/dot;
dot*=10;
}
}
else
if((c=='.')&&(dot==0))
dot=10;
else
if(c!='\n')
success=1;
}while((c!='\n')&&(succes==0));
if(success!=0) return -1; //error we break out
if(base<.5)
printf("Invalid Input\n");
while (base<.5)
return 0;
if(base>100)
printf("Invalid Input\n");
while(base>100)
return 0;
printf("Please enter the value of height of the triangle:\n");
c='\n';
success=0;
height=0;
dot=0;
do{
scanf ("%c", &c);
if((c>=48)&&(c<=57)){
if(dot==0)
height=height*10+(c-48);
else{
height+=(c-48)/dot;
dot*=10;
}
}
else
if((c=='.')&&(dot==0))//check if is the first time the user insert a dot
dot=10;
else
if(c!='\n')
success=1;
}while((c!='\n')&&(succes==0));
if(success!=0) return -1; //error we break out
if(height<1)
printf("Invalid Input\n");
while(height<1)
return 0;
if(height>75)
printf("Invalid Input\n");
while (height>75)
return 0;
area = base * height/2;
printf("The area of the triangle for base: %f and height: %f is %f \n", base,
height , area );
return 0;
}
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