1108 Finding Average （20 分）

最新推荐文章于 2024-07-02 17:41:22 发布

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最新推荐文章于 2024-07-02 17:41:22 发布

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分类专栏： PAT甲级(Advanced Level) 文章标签： PAT

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本文介绍了一种算法，用于从一组输入数据中筛选出合法的数值，并计算这些数值的平均值。合法数值定义为范围在[-1000,1000]内的实数，且精度不超过两位小数。文章提供了具体的输入输出规范，以及如何使用sscanf和sprintf函数判断数值合法性。

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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:

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

使用：sscanf（）和sprintf() 一个用于格式化从字符串中读入变量，一个用于格式化从变量输出到字符串中，若二个字符串比较不相等，等说明不合法。

#include<iostream>
#include<string>
#include<stdio.h>
#include<string.h>
#include<vector>
#include<set>
#include<map>
#include<unordered_map>
#include<queue>
#include<algorithm>
#include<cmath>
using namespace std;
#define ll long long
#define vi vector<int>
#define pii pair<int, int>
#define x first
#define y second
const int maxn=110;
int n,cnt=0;
int main()
{
    cin>>n;
    double temp,res=0;
    char a[maxn],b[maxn];
    for(int i=0;i<n;i++)
    {
        scanf("%s",a);
        sscanf(a,"%lf",&temp);
        sprintf(b,"%.2f",temp);
        int flag=0;
        for(int j=0;j<strlen(a);j++){
             if(a[j]!=b[j]) flag=1;
        }
        if(flag ||temp<-1000|| temp>1000)
        {
            printf("ERROR: %s is not a legal number\n",a);
            continue;
        }
        else
        {
            res+=temp;
            cnt++;
        }
    }
    if(cnt==1)
      printf("The average of 1 number is %0.2f\n",res);
    else if(cnt>1)
      printf("The average of %d numbers is %0.2f\n",cnt,res/cnt);
    else
      printf("The average of 0 numbers is Undefined");
    return 0;
}