leetcode- First Bad Version---简单

# The isBadVersion API is already defined for you.
# @param version, an integer
# @return a bool
# def isBadVersion(version):

class Solution(object):
def firstBadVersion(self, n):
"""
:type n: int
:rtype: int
"""

i = 1
j = n
while i <= j:
mid = int(float(i + j )/2)
a = isBadVersion(mid)

if a:
j = mid - 1
else:
i = mid + 1

return i