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107中央資工解遞迴
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JoyceTsai
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Jan 1, 2020, 11:04:12 AM
1/1/20
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to 黃子嘉 - 線代離散研究室
請問,
此題詳解倒數第四行的地方,為什麼取n=4^k來解遞迴?
也看不懂為什麼帶入之後會變成Xk=2xk-1+2^k
麻煩了qq
蘇家輝
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Jan 2, 2020, 12:51:15 AM
1/2/20
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to 黃子嘉 - 線代離散研究室
代入4^k是為了滿足遞迴的特徵,因為4^k除4就會變成4^(k-1),
然後因為 x(k) = 4^k
所以 x(k-1) = 4 ^ ( k-1 ),x(k-2) = 4 ^ ( k-2 )......
sqrt ( n ) = 2^k,因為在看複雜度 sqrt ( n/4 )不大於 sqrt ( n )所以後面可以不寫,
代入原式就會有那個答案
在這裡把遞迴的數列看成一般函數會比較好懂
JoyceTsai
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Jan 2, 2020, 1:47:42 AM
1/2/20
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to 黃子嘉 - 線代離散研究室
了解,謝謝您!
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