35 lines
531 B
Python
35 lines
531 B
Python
'''
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【程序24】
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题目：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。
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1.程序分析：请抓住分子与分母的变化规律。
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2.程序源代码：
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'''
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#方法一
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a = 2.0
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b = 1.0
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s = 0
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for n in range(1,21):
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s += a / b
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t = a
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a = a + b
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b = t
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print s
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#方法二
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s = 0.0
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for n in range(1,21):
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s += a / b
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b,a = a , a + b
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print s
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s = 0.0
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for n in range(1,21):
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s += a / b
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b,a = a , a + b
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print s
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#方法三
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l = []
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for n in range(1,21):
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b,a = a,a + b
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l.append(a / b)
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print reduce(lambda x,y: x + y,l)
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