1108 Finding Average

link

#include <iostream>
#include <cstring>
#include <queue>
#include <cmath>
#include <unordered_map>
#include <algorithm>
#include <stack>
# define LL long long
using namespace std;


int N;
double candi;
bool valid(string s){
    int flag=1;
    if(s[0]=='-'){
        if(s.size()==1){
            return false;
        }
        flag=-1;
        s=s.substr(1,s.size()-1);
    }
    int dot=0;
    for(int j=0;j<s.size();j++){
        if(s[j]=='.') dot++;
        if(!( (s[j]>='0' && s[j]<='9') || s[j]=='.' )){
            return false;
        }
    }
    if(dot>1){
        return false;
    }
    int dotpos=-1;
    for(int j=0;j<s.size();j++){
        if(s[j]=='.'){
            dotpos=j;
            break;
        }
    }
    if(dotpos==-1){
        if(s.size()>4){
            return false;
        }
        int num=stoi(s);
        if(num<=1000){
            candi=flag*num;
        }else{
            return false;
        }
    }else{
        int rightpart=s.size()-1-dotpos;
        int leftpart=dotpos;
        if(rightpart>2 || leftpart>4){
            return false;
        }else if(dotpos==s.size()-1){
            int num=stoi(s.substr(0,s.size()-1));
            candi=1.0*flag*num;

        }else if(dotpos==0){
            int rightnum=stoi(s.substr(dotpos+1,rightpart));
            candi=flag*(1.0*rightnum/pow(10,rightpart));
        }
        else{
            int leftnum=stoi(s.substr(0,dotpos));
            int rightnum=stoi(s.substr(dotpos+1,rightpart));
            candi=flag*(1.0*leftnum+1.0*rightnum/pow(10,rightpart));
        }
        if(candi<-1000.0 || candi>1000.0){
            return false;
        }
    }
    return true;
};

int main(){
    scanf("%d", &N);
    int ilcnt=0;
    double res=0.0;
    for(int i=0;i<N;i++){
        string s;
        cin>>s;
        bool r=valid(s);
        if(!r){
            cout<<"ERROR: "<<s<<" is not a legal number"<<"
";
            ilcnt++;
        }else{
            res+=candi;
        }
    }

    if(ilcnt==N){
        printf("The average of 0 numbers is Undefined
");
    }else if(N-ilcnt>1){
        double avg=res/(N-ilcnt);
        printf("The average of %d numbers is %.2f
", N-ilcnt, avg);
    }else{
        double avg=res/(N-ilcnt);
        printf("The average of %d number is %.2f
", N-ilcnt, avg);
    }
    return 0;
}

利用 sscanf, sprintf :

#include <iostream>
#include <cstring>
#include <queue>
#include <cmath>
#include <unordered_map>
#include <algorithm>
#include <stack>
# define LL long long
using namespace std;


int N;

char a[50], b[50];
double candi;
int main(){
    scanf("%d", &N);
    int ilcnt=0;
    double res=0.0;
    for(int i=0;i<N;i++){
        int flag=1;
        scanf("%s", a);
        sscanf(a,"%lf",&candi);
        sprintf(b,"%.2f", candi);
        for(int j=0;j<strlen(a);j++){
            if(a[j]!=b[j]){
                flag=0;
                break;
            }
        }
        if(flag==0 || candi<-1000 || candi>1000){
            ilcnt++;
            printf("ERROR: %s is not a legal number
", a);
        }else{
            res+=candi;
        }
    }

    if(ilcnt==N){
        printf("The average of 0 numbers is Undefined
");
    }else if(N-ilcnt>1){
        double avg=res/(N-ilcnt);
        printf("The average of %d numbers is %.2f
", N-ilcnt, avg);
    }else{
        double avg=res/(N-ilcnt);
        printf("The average of %d number is %.2f
", N-ilcnt, avg);
    }
    return 0;
}