一、题目描述
原题链接
Input Specification:
Output Specification:
Sample Input 1:
7 5 -3.2 aaa 9999 2.3.4 7.123 2.35
Sample Output 1:
ERROR: aaa is not a legal number ERROR: 9999 is not a legal number ERROR: 2.3.4 is not a legal number ERROR: 7.123 is not a legal number The average of 3 numbers is 1.38
Sample Input 2:
2 aaa -9999
Sample Output 2:
ERROR: aaa is not a legal number ERROR: -9999 is not a legal number The average of 0 numbers is Undefined
二、解题思路
这道题纯用字符串处理还是比较麻烦的，但是如果掌握了sscanf和sprintf函数的话，就可以很简便地解决了，我的代码是比较复杂的，看个乐子就行… 建议大家看看柳神的代码： 1108. Finding Average (20)-PAT甲级真题
三、AC代码
#include<iostream>
#include<string>
#include<algorithm>
#include<cstdio>
#include<vector>
#include<cmath>
using namespace std
;
vector
<double> valid
;
double to_num(string str
)
{
int sze
= str
.size(), st
;
bool flagdot
= false;
int posdot
= -1;
double ans
= 0.0;
double acc
= 0.0;
if(str
[0] == '-') st
= 1;
else st
= 0;
for(int i
=st
; i
<sze
; i
++)
{
if(str
[i
] == '.')
{
flagdot
= true;
posdot
= i
;
continue;
}
if(flagdot
)
acc
= acc
*10 + str
[i
] - '0';
else
ans
= ans
*10 + str
[i
] - '0';
}
if(flagdot
) sze
-1-posdot
== 2 ? acc
*= 0.01 : acc
*= 0.1;
ans
+= acc
;
if(st
== 1) ans
= -ans
;
return ans
;
}
bool check(string str
)
{
int sze
= str
.size(), cntdots
= 0, posdot
;
if(str
[0] == '.') return false;
if(sze
== 1 && !(str
[0]>='0' && str
[0]<='9')) return false;
for(int i
=0; i
<sze
; i
++)
{
if(str
[i
] >= '0' && str
[i
] <= '9')
continue;
else
{
if(i
==0 && str
[i
] == '-') continue;
if(str
[i
] == '.')
{
cntdots
++;
posdot
= i
;
}
else return false;
}
if(cntdots
> 1) return false;
}
if(cntdots
== 1 && sze
- posdot
- 1 > 2) return false;
double num
= to_num(str
);
if(num
< -1000.0 || num
> 1000.0) return false;
else return true;
}
int main()
{
string str
;
int N
;
scanf("%d", &N
);
for(int i
=0; i
<N
; i
++)
{
cin
>> str
;
if(check(str
))
valid
.push_back(to_num(str
));
else
cout
<< "ERROR: " << str
<< " is not a legal number" << endl
;
}
double sum
=0.0, avg
;
int sze
= valid
.size();
if(sze
== 1)
{
printf("The average of 1 number is %.2f\n", valid
[0]);
return 0;
}
else if(sze
== 0)
printf("The average of 0 numbers is Undefined\n", sze
);
else
{
for(int i
=0; i
<sze
; i
++)
sum
+= valid
[i
];
avg
= sum
/sze
;
printf("The average of %d numbers is %.2f\n", sze
, avg
);
}
return 0;
}
