The basic task is simple: given N real numbers, you are supposed to calculate their average. But what makes it complicated is that some of the input numbers might not be legal. A “legal” input is a real number in [-1000, 1000] and is accurate up to no more than 2 decimal places. When you calculate the average, those illegal numbers must not be counted in.
Input Specification:
Each input file contains one test case. For each case, the first line gives a positive integer N (<=100). Then N numbers are given in the next line, separated by one space.
Output Specification:
For each illegal input number, print in a line “ERROR: X is not a legal number” where X is the input. Then finally print in a line the result: “The average of K numbers is Y” where K is the number of legal inputs and Y is their average, accurate to 2 decimal places. In case the average cannot be calculated, output “Undefined” instead of Y. In case K is only 1, output “The average of 1 number is Y” instead.
Sample Input 1:
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1 2 |
7 5 -3.2 aaa 9999 2.3.4 7.123 2.35 |
Sample Output 1:
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1 2 3 4 5 |
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:
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1 2 |
2 aaa -9999 |
Sample Output 2:
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1 2 3 |
ERROR: aaa is not a legal number ERROR: -9999 is not a legal number The average of 0 numbers is Undefined |
今天中午和下午抽空把 PAT-Advanced 新增的题都做掉了，感觉难度都好一般。但是自己最近的码力确实是下降了，容易犯一些低级的错误，思路也不够清晰了。
这道题需要注意的是最多精确到 2 位，同时只有 0 个或 1 个合法数字时的输出。（似乎和测试点 3 有关
In case the average cannot be calculated, output “Undefined” instead of Y. In case K is only 1, output “The average of 1 number is Y” instead.
其他的就没有什么问题，就是发现自己的思路好不清晰，写第一遍时没有 AC ，然后偷懒直接 sscanf 反而过了……
本来打算写一个基于正则表达式的，但不知 regex.h 能不能用，回来有空尝试一下。
代码如下：
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#include<stdio.h> #include<stdlib.h> #define DOT 1 #define SIGN 2 #define INT 4 #define FLOAT 8 #define LARGE 16 int check(char *buf) { int flag=0,i,count,temp; char dot; for(i=0;buf[i];i++) { switch(buf[i]) { case '.': if(flag&DOT) { return 0; } else { flag=flag|DOT; } break; case '+': case '-': if(flag&SIGN||flag&DOT) { return 0; } else { flag=flag|SIGN; } break; default: if(!(buf[i]>='0'&&buf[i]<='9')) { return 0; } } } for(i=0;buf[i]!='.'&&buf[i]!=0;i++) { ; } count=0; for(i;buf[i];i++) { count++; } if(count>3) { return 0; } return 1; /* for(i=0;buf[i]!='.'&&buf[i]!=0;i++)//之前写的测试过程 { ; } dot=buf[i]; buf[i]=0; sscanf(buf,"%d",&temp); buf[i]=dot; if(temp>1000||temp<-1000) { return 0; } if(buf[i]==0) { return 1; } if(temp==1000||temp==-1000) { flag=flag|LARGE; } temp=0; buf[i]='0'; sscanf(buf+i,"%d",&temp); buf[i]=dot; count=0; for(i++;buf[i];i++) { count++; } if(count>2) { return 0; } if((flag&LARGE)&&temp==0||temp<100&&(flag&LARGE)==0) { return 1; } else { return 0; }*/ } int main() { int n,i,total=0; double sum=0,temp; char buf[101]; scanf("%d",&n); for(i=0;i<n;i++) { scanf("%s",buf); if(check(buf)) { sscanf(buf,"%lf",&temp); if(temp<=1000.00&&temp>=-1000.00) { sum+=temp; total++; } else { printf("ERROR: %s is not a legal number\n",buf); } } else { printf("ERROR: %s is not a legal number\n",buf); } } if(total==0) { printf("The average of 0 numbers is Undefined\n"); } else if(total==1) { printf("The average of %d number is %.2lf\n",total,sum); } else { printf("The average of %d numbers is %.2lf\n",total,sum/total); } } |