For example,in most sub-Saharan African countries, the U.N.Children's Fund says more than half the deliveries take place at home, with no skilled birth attendant present.

VOA: standard.2010.05.11

Log n Log n, because at each stage I'm cutting the problem in half. So I start off with n then it's n n/2 n/4 n/8 over two n over four n over eight.

因为总共有多少层？,因为在每一层，我都是把问题分解成两半,因此以n开始，然后是。

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