leetcode 374. Guess Number Higher or Lower

We are playing the Guess Game. The game is as follows:

 

I pick a number from 1 to n. You have to guess which number I picked.

Every time you guess wrong, I'll tell you whether the number is higher or lower.

You call a pre-defined API guess(int num) which returns 3 possible results (-1, 1, or 0):

-1 : My number is lower
 1 : My number is higher
 0 : Congrats! You got it!

Example:

n = 10, I pick 6.

Return 6.

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

# The guess API is already defined for you. # @param num, your guess # @return -1 if my number is lower, 1 if my number is higher, otherwise return 0 # def guess(num):   class Solution(object):     def guessNumber(self, n):         """         :type n: int         :rtype: int         """         #1 <= x <= n         i, j = 1, n         while i<=j:             mid = (i+j)>>1             r = guess(mid)             if r == 0:                 return mid             elif r == 1:                 i = mid+1             else:                 j = mid-1                        #return -1?

 注意："mid = (high + low) / 2;"

 lign + low => int + int --->it may cause overflow~
Interger scale [-2^31,2^31]

所以一般： int mid = start+(end-start)/2;

如果是c++代码要当心！