PTA 乙级 1054 求平均值 (20分) C/C++

 主要还是两个函数的使用：sscanf 和 sprintf

sscanf

 int sscanf（const char * s，const char * format，...）; 

sprintf

 int sprintf（char * str，const char * format，...）; 

#include<iostream>
#include<cstring>
using namespace std;

int main() {
    int n = 0, k = 0;
    float sum = 0;
    cin >> n;
    for (int i = 0; i < n; ++i) {
        char s1[100], s2[100];                    //一定要定义足够大，否则会出现测试点2运行时错误
        float num = 0.0;
        cin >> s1;
        sscanf(s1, "%f", &num);                    //将s1中浮点数写入num
        sprintf(s2, "%.2f", num);                //num保留两位数字输出到s2
        if (strncmp(s1, s2, strlen(s1)) == 0 && (num <= 1000 && num >= -1000)) {    //利用strncmp，防止读取s2中多余的0
            sum += num;
            k++;
        }
        else {
            cout << "ERROR: " << s1 << " is not a legal number" << endl;
        }
    }
    if (k == 0) cout << "The average of 0 numbers is Undefined";
    else if (k == 1) printf("The average of 1 number is %.2f", sum / k);    //注意只有一个数字的情况
    else printf("The average of %d numbers is %.2f", k, sum / k);
    return 0;
}