1108. Finding Average (20)-PAT甲级真题

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

分析：用非常好用的sscanf和sprintf即可解决～
sscanf() – 从一个字符串中读进与指定格式相符的数据
sprintf() – 字符串格式化命令，主要功能是把格式化的数据写入某个字符串中

#include <iostream>
#include <cstdio>
#include <string.h>
using namespace std;
int main() {
    int n, cnt = 0;
    char a[50], b[50];
    double temp = 0.0, sum = 0.0;
    cin >> n;
    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 {
            sum += temp;
            cnt++;
        }
    }
    if(cnt == 1)
        printf("The average of 1 number is %.2f", sum);
    else if(cnt > 1)
        printf("The average of %d numbers is %.2f", cnt, sum / cnt);
    else
        printf("The average of 0 numbers is Undefined");
    return 0;
}

#include <iostream>

#include <cstdio>

#include <string.h>

using namespace std;

int main() {

int n, cnt = 0;

char a[50], b[50];

double temp = 0.0, sum = 0.0;

cin >> n;

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 {

sum += temp;

cnt++;

}

if(cnt == 1)

printf("The average of 1 number is %.2f", sum);

else if(cnt > 1)

printf("The average of %d numbers is %.2f", cnt, sum / cnt);

else

printf("The average of 0 numbers is Undefined");

return 0;

}

❤ 点击这里 -> 订阅《PAT | 蓝桥 | LeetCode学习路径 & 刷题经验》by 柳婼

❤ 点击这里 -> 订阅《从放弃C语言到使用C++刷算法的简明教程》by 柳婼

❤ 点击这里 -> 订阅PAT甲级乙级、蓝桥杯、GPLT天梯赛、LeetCode题解离线版