(PAT 1108) Finding Average (字符串处理)

蔚落 2022-03-19 03:58 144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;
    }