First Bad Version
You are a product manager and currently leading a team to develop a new product. Unfortunately, the latest version of your product fails the quality check. Since each version is developed based on the previous version, all the versions after a bad version are also bad.
Suppose you haven
versions[1, 2, ..., n]
and you want to find out the first bad one, which causes all the following ones to be bad.
You are given an APIbool isBadVersion(version)
which will return whetherversion
is bad. Implement a function to find the first bad version. You should minimize the number of calls to the API.
分析
二分
往后都是bad,所以每次移动end,然后判断start,再end
/* The isBadVersion API is defined in the parent class VersionControl.
boolean isBadVersion(int version); */
public class Solution extends VersionControl {
public int firstBadVersion(int n) {
int s = 1, e = n;
while(s + 1 < e){
int m = s + (e - s)/2;
if(isBadVersion(m)){
e = m;
}else{
s = m;
}
}
if(isBadVersion(s))
return s;
else
return e;
}
}
class Solution:
def firstBadVersion(self, n):
"""
:type n: int
:rtype: int
"""
s,e=0,n
while s+1<e:
m = s+(e-s)//2
if isBadVersion(m):
e = m
else:
s = m
return s if isBadVersion(s) else e
花花木板 左闭右开
class Solution:
def firstBadVersion(self, n):
"""
:type n: int
:rtype: int
"""
s,e = 1,n#因为是开区间,所以应该是N+1,但是怕溢出。
while s < e:
m = s + (e-s)//2
if isBadVersion(m):
e = m
else:
s = m + 1
return s
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