PAT甲级——1108 Finding Average (字符串)

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最新推荐文章于 2024-07-02 17:41:22 发布

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博客围绕计算合法数字平均值展开。给定N个实数，合法输入需是[-1000, 1000]内且精确到不超2位小数的实数。要找出合法数字，排除非法数字，最后计算合法数字的平均值并保留两位小数输出。

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1108 Finding Average (20 分)

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

题目大意：找出给的数据中合法的数字（ [-1000, 1000] ），计算平均值输出，保留两位小数。

思路：读取字符串，判断是不是数字，找全判断条件就可以了。

#include <iostream>
#include <string>
using namespace std;
bool isLegal(string &s, float &num);
bool isChar(char c);
int main()
{
	int N, cnt = 0;
	float sum = 0;
	string s;
	scanf("%d", &N);
	for (int i = 0; i < N; i++) {
		cin >> s;
		float num;
		if (isLegal(s, num)){
			sum += num;
			cnt++;
		}
		else {
			printf("ERROR: ");
			cout << s;
			printf(" is not a legal number\n");
		}
	}
	if (cnt > 1)
		printf("The average of %d numbers is %.2f\n", cnt, sum / cnt * 1.0);
	else if (cnt == 1)
		printf("The average of 1 number is %.2f\n", sum);
	else
		printf("The average of 0 numbers is Undefined\n");
	return 0;
}
bool isLegal(string &s, float &num) {
	bool flag = false;
	int cnt1 = 0, cnt2 = 0;//分别记录'.'和小数部分的数字数量
	if (s[0] == '-')
		flag = true;
	for (int i = 0; i < s.length(); i++) {
		if (flag) {
			flag = false;
			continue;
		}
		if (isChar(s[i]) && s[i] != '.')
			return false;
		else if (s[i] == '.') {
			cnt1++;
			if (cnt1 > 1)
				return false;
		}
		else if (cnt1 == 1) {
			cnt2++;
			if (cnt2 > 2)
				return false;
		}
	}
	num = stof(s);
	return (num >= -1000 && num <= 1000) ? true : false;
}
bool isChar(char c) {
	if (c >= '0'&&c <= '9')
		return false;
	else
		return true;
}