1108 Finding Average
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 [−] 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 (≤). 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
思路:
格式化输入,输出
sscanf() : C 库函数 int sscanf(const char *str, const char *format, ...) 从字符串读取格式化输入。
sprintf() : C 库函数 int sprintf(char *str, const char *format, ...) 发送格式化输出到 str 所指向的字符串。
因为这两个库都是C语言里面的,所以对string好像不太好用,写的时候写成char[]来表示string。
Code:
#include <bits/stdc++.h> using namespace std; int main() { int n; cin >> n; int count = 0; char in[50], out[50]; double temp, sum = 0.0; for (int i = 0; i < n; ++i) { scanf("%s", in); sscanf(in, "%lf", &temp); sprintf(out, "%.2f", temp); bool isLegal = false; for (int j = 0; j < strlen(in); ++j) { if (in[j] != out[j]) { isLegal = true; } } if (isLegal || temp > 1000 || temp < -1000) { printf("ERROR: %s is not a legal number\n", in); } else { sum += temp; count++; } } if (count == 1) printf("The average of 1 number is %.2f", sum); else if (count > 1) { double average = sum / count; printf("The average of %d numbers is %.2f", count, average); } else { printf("The average of 0 numbers is Undefined"); } return 0; }
参考: https://www.liuchuo.net/archives/1924
对于这种题一定要认真读题,不要被以前做过的题给绑架了。