北大POJ解题报告-1004 Financial Management

Description

Larry graduated this year and finally has a job. He's making a lot of money, but somehow never seems to have enough. Larry has decided that he needs to grab hold of his financial portfolio and solve his financing problems. The first step is to figure out what's been going on with his money. Larry has his bank account statements and wants to see how much money he has. Help Larry by writing a program to take his closing balance from each of the past twelve months and calculate his average account balance.

Input

The input will be twelve lines. Each line will contain the closing balance of his bank account for a particular month. Each number will be positive and displayed to the penny. No dollar sign will be included.

Output

The output will be a single number, the average (mean) of the closing balances for the twelve months. It will be rounded to the nearest penny, preceded immediately by a dollar sign, and followed by the end-of-line. There will be no other spaces or characters in the output.

Sample Input

100.00
489.12
12454.12
1234.10
823.05
109.20
5.27
1542.25
839.18
83.99
1295.01
1.75

Sample Output

$1581.42

描述：求一下Larry一遍12个月的平均存款余额

可能的难点：对于有效数字的处理

知识点：

使用setprecision(n)可控制输出流显示浮点数的数字个数。C++默认的流输出数值有效位是6。
  如果setprecision(n)与setiosflags(ios::fixed)合用，可以控制小数点右边的数字个数。setiosflags(ios::fixed)是用定点方式表示实数。 
  如果与setiosnags(ios::scientific)合用， 可以控制指数表示法的小数位数。setiosflags(ios::scientific)是用指数方式表示实数。

更多参考：http://blog.youkuaiyun.com/slience_perseverance/article/details/6816904

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

int main()
{
	float c = 0,sum = 0;
	int count = 0;
	while(count++<12 && cin>>c)
	{
		sum += c;
	}
	cout<<fixed<<setprecision(2);
	cout<<"$"<<(float)sum/12<<endl;
	return 0;
}