leetcode- First Bad Version---简单

https://leetcode.com/problems/first-bad-version/

binary search

my code:

# 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