2014
01-05

# Savings Account

Suppose you open a savings account with a certain initial balance. You will not make any withdrawals or further deposits for a number of years. The bank will compound your balance (add the annual interest) once a year, on the anniversary of the opening of the account. Your goal is to achieve a certain target amount in your savings account. In how may years will the target amount be achieved?

The input file will contain data for one or more test cases, one test case per line. Each line will contain three numbers: the initial balance, the annual interest rate (as a percentage of the balance), and the target amount, separated by blank spaces. These will be positive numbers; they may or may not contain a decimal point. The target amount will be greater than the initial balance. The input is terminated by end-of-file

The input file will contain data for one or more test cases, one test case per line. Each line will contain three numbers: the initial balance, the annual interest rate (as a percentage of the balance), and the target amount, separated by blank spaces. These will be positive numbers; they may or may not contain a decimal point. The target amount will be greater than the initial balance. The input is terminated by end-of-file

200.00 6.5 300
500 4 1000.00

7
18

/*
hdu	2398 Savings Account - 数学
*/
#include<iostream>
#include<cmath>
using namespace std;
int main()
{
double x,y,a,l;
int ret;
while(cin>>x>>l>>y)
{
l=1+l/100;
a=log(y/x)/log(l);//l^a=y/x
ret=ceil(a);//向上取整  floor是向下
cout<<ret<<endl;
}
return 0;
}

1. 学算法中的数据结构学到一定程度会乐此不疲的，比如其中的2－3树，类似的红黑树，我甚至可以自己写个逻辑文件系统结构来。