Question

3.20 编程计算并输出 1+1/2+2/3+3/5+……前20项的和.

Answer 1

# 使用Python实现
>>> i, j, count, sum = 1, 1, 0, 0 # 分子、分母、计数器、和
>>> while count <= 20:
... sum += i*1.0 / j # 求和
... print 'i=%d, j=%d, sum=%f' % ( i, j, sum ) # 打印输出
... i, j = j, i+j # 分子、分母递进
... count += 1 # 计数器累加
...
i=1, j=1, sum=1.000000
i=1, j=2, sum=1.500000
i=2, j=3, sum=2.166667
i=3, j=5, sum=2.766667
i=5, j=8, sum=3.391667
i=8, j=13, sum=4.007051
i=13, j=21, sum=4.626099
i=21, j=34, sum=5.243746
i=34, j=55, sum=5.861928
i=55, j=89, sum=6.479905
i=89, j=144, sum=7.097961
i=144, j=233, sum=7.715987
i=233, j=377, sum=8.334024
i=377, j=610, sum=8.952057
i=610, j=987, sum=9.570091
i=987, j=1597, sum=10.188125
i=1597, j=2584, sum=10.806159
i=2584, j=4181, sum=11.424193
i=4181, j=6765, sum=12.042227
i=6765, j=10946, sum=12.660261
i=10946, j=17711, sum=13.278295
>>>

Answer 2

<script>
var j=0;
for(var i=1;i<=20;i++){
j+=i+i;
}
alert(j);
</script>
js