PTA乙级题 1054. 求平均值 (20)

【题目链接】

用C++判断是否为数字。

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
char str[110][1100];
int main(){
    int n;
    int count=0;
    double average=0;
    scanf("%d",&n);
    for(int i=0;i<n;i++)
    {
        bool isNumber=true;
        int dot=0;
        int dotnum=0;
        scanf("%s",str[i]);
        int len=strlen(str[i]);
        for(int j=0;j<len;j++)
        {
            if(dot==1)
            dotnum++;
            if(str[i][j]=='-'&&j!=0)
            {
                isNumber=false;
                break;
            }
            if(str[i][j]=='.')
            dot++;
            else
            {
                if((str[i][j]<'0'||str[i][j]>'9')&&(str[i][j]!='-'))
                {
                    isNumber=false;
                    break;
                }
            }
            if(dot>=2||dotnum>=3)
            {
                isNumber=false;
                break;
            }   
        }
        double num=atof(str[i]);
        if(num>1000||num<-1000)
        isNumber=false;
        if(isNumber)
        {
            count++;
            average+=num;
        }
        else
        printf("ERROR: %s is not a legal number\n",str[i]);
    }
    if(count==0)
        printf("The average of 0 numbers is Undefined");
    else if(count==1)
        printf("The average of %d number is %.2f",count,average);
    else 
        printf("The average of %d numbers is %.2f",count,average/count);
    return 0;
}