Rational Resistance
CodeForces - 344CMad scientist Mike is building a time machine in his spare time. To finish the work, he needs a resistor with a certain resistance value.
However, all Mike has is lots of identical resistors with unit resistance R0 = 1. Elements with other resistance can be constructed from these resistors. In this problem, we will consider the following as elements:
- one resistor;
- an element and one resistor plugged in sequence;
- an element and one resistor plugged in parallel.
With the consecutive connection the resistance of the new element equals R = Re + R0. With the parallel connection the resistance of the new element equals . In this case Re equals the resistance of the element being connected.
Mike needs to assemble an element with a resistance equal to the fraction . Determine the smallest possible number of resistors he needs to make such an element.
Input
The single input line contains two space-separated integers a and b (1 ≤ a, b ≤ 1018). It is guaranteed that the fraction is irreducible. It is guaranteed that a solution always exists.
Print a single number — the answer to the problem.
Please do not use the %lld specifier to read or write 64-bit integers in С++. It is recommended to use the cin, cout streams or the %I64d specifier.
Examples1 1
1
3 2
3
199 200
200
In the first sample, one resistor is enough.
In the second sample one can connect the resistors in parallel, take the resulting element and connect it to a third resistor consecutively. Then, we get an element with resistance . We cannot make this element using two resistors.
这是一道很骚的高中的物理题,要求给你a,b两个数,用最少个数的1欧姆电阻通过串联或者并联的方式得到电阻大小为a/b
根据并联电阻的公式,一、如果a/b大于1,肯定要先串联(int)(a/b)个,
二、剩下的真分数部分a'/b'肯定是需要我们并联得到,那么这部分电阻a'/b' = 1/(b'/a'),
此时b'/a'又是一个假分数,和一开始情形一样了那么继续重复执行步骤1,直到分子为1,最后加上分子为1时那个分数的分母,就是总共需要最小的电阻数
就拿样例3来说199/200的电阻,我们先取倒数得到200/199 = 1 + 1/199,所以我们需要199个1欧姆电阻并联,得到1/199欧
然后1欧的再和1/199欧的并联得到答案也就是 199/200 = 1/(1+1/199)
code:
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
typedef long long ll;
int main(){
ll a,b;
ll ans = 0;
scanf("%lld%lld",&a,&b);
ans += (a / b);
a = a % b;
if(a == 0){//如果整除,那么说明都是串联的
printf("%lld\n",ans);
return 0;
}
while(a != 1){
swap(a,b);
ans += (a / b);
a = a % b;
if(a == 0) break;
}
if(a == 1) ans += b;
printf("%lld\n",ans);
return 0;
}