#Leet Code# Sqrt

描述：log(n)

代码：

 1 class Solution:
 2     # @param x, an integer
 3     # @return an integer
 4     def getVal(self, begin, end, x):
 5         if end == begin :
 6             return begin
 7         if end == begin + 1:
 8             return begin
 9
10         while True:
11             mid = (begin + end) / 2
12             tmp = mid * mid
13
14             if tmp == x:
15                 return mid
16             elif tmp < x:
17                 return self.getVal(mid, end, x)
18             elif tmp > x:
19                 return self.getVal(begin, mid, x)
20
21     def sqrt(self, x):
22         if x == 0: return 0
23
24         val = 1
25         while True:
26             tmp  = val * val
27
28             if tmp == x:
29                 return val
30             elif tmp > x:
31                 return self.getVal(val/2, val, x)
32             else:
33                 val *= 2

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