Question

java编程题 有一分数序列：2/1，3/2，5/3，8/5，13/8，21/13...求出这个数列的前20项之和。

Answer 1

public class Shulie {

public static void main(String[] args) {

int fenzi = 1;
int fenmu = 2;

double sum = 0.0D;

int count = 1;

while(count <= 20){

if(count == 1){
sum += (double) fenmu /fenzi;
}else{
int temp = fenmu;
fenmu = fenzi + fenmu;
fenzi = temp;

sum += (double) fenmu/fenzi;
}

count++;
}

System.out.println("2/1 + 3/2 + 5/3 + ... + " + fenzi + "/" + fenmu + "=" + sum);

}

}

-----------------testing
2/1 + 3/2 + 5/3 + ... + 10946/17711=32.66026079864164

Answer 2

递归算法。很简单。
public class display{
public double sum;
public void plus(int fenzi,int fenmu,int num){
if(num>0)
{
sum += 1.0*fenzi/fenmu;
plus(fenzi+fenmu,fenzi,num-1);
}
}
public static void main(String args[]){
display aa = new display();
aa.sum = 0;
aa.plus(2,1,20);
System.out.println("sum is " + aa.sum);

}
}

Answer 3

public static void main(String[] args) {
int a=2;//分子
int b=1;//分母
double sum=0;//结果
for(int i=1;i<=20;i++){
sum+=a/b;
int c=js(a,b);
b=a;
a=c;
}
System.out.println(sum);

}
public static int js(int a,int b){
int s=a+b;
return s;
}

Answer 4

public void sum20(){
double sum = 21;
int count = 1;
int first = 1, second = 2;
while(count<20){
sum += first/second;
second += first;
first = second - first;
count++;
}
return sum;
}

Answer 5

public class TestNum {
public static void main(String[] args) {
float fm = 1f;
float fz = 1f;
float temp;
float sum = 0f;
for (int i=0;i<20;i++){
temp = fm;
fm = fz;
fz = fz + temp;
sum += fz/fm;
}
System.out.println(sum);
}
}