(PAT 1108) Finding Average (字符串处理)-蒲公英云

(PAT 1108) Finding Average (字符串处理)

蔚落 2022-03-19 03:58 220阅读 0赞

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

解题思路:

直接无脑if else就行了,这里的坑点是要仔细读题,注意最后的number和numbers！

关于string转float 用stof就可以了

#include <iostream>
#include <algorithm>
#include <string>
using namespace std;
int N;
int main() {
    cin >> N;
    string tnum;
    float sum = 0.0;
    int nn = 0;
    for (int i = 0; i < N; ++i) {
        int countpoint = 0;
        bool countpointDug = true;
        bool islegal = true;
        int numbernum = 0;
        int countnumber = 0;
        bool zeroflag = true;
        cin >> tnum;
        for (int j = 0; j < tnum.length(); ++j) {
            //判断负号
            if (tnum[j] == '-') {
                if (j == 0) {
                    continue;
                }
                else {
                    islegal = false;
                    break;
                }
            }
           //判断小数点
            if (tnum[j] == '.') {
                countpoint++;
                if (countpoint > 1) {
                    islegal = false;
                    break;
                }
                continue;
            }
            //判断是否是字符
            if (tnum[j] >= 0 + '0' && tnum[j]  <= 9 + '0') {
                numbernum++;
                if (countpoint == 1) countnumber++;
                if (countpoint == 0 && numbernum > 4) {
                    islegal = false;
                    break;
                }
                if (countpoint == 1 && countnumber > 2) {
                    islegal = false;
                    break;
                }
            }
            else {
                islegal = false;
                break;
            }
        }
        if (!islegal) {
            cout << "ERROR: "<<tnum<<" is not a legal number" << endl;
        }
        else {
            float dres = stof(tnum);
            if(dres<-1000 || dres > 1000) cout << "ERROR: " << tnum << " is not a legal number" << endl;
            else {
                sum += dres;
                nn++;
            }
        }
    }
    if (nn == 0) {
        printf("The average of 0 numbers is Undefined\n");
    }
    else if (nn == 1) {
        printf("The average of 1 number is %.2f\n",sum);  //坑点在这里！！请仔细读题
    }
    else{
        printf("The average of %d numbers is %.2f", nn, sum / nn);
    }
    return 0;
}