278 First Bad Version

基础二分搜索。标准的二分

Python

# 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
        """
        l, r = 1, n
        while l <= r:
            mid = l + (r-l)//2
            if isBadVersion(mid):
                r = mid - 1
            else:
                l = mid + 1
        return l

Java

public int firstBadVersion(int n) {
    int left = 1;
    int right = n;
    while (left < right) {
        int mid = left + (right - left) / 2;
        if (isBadVersion(mid)) {
            right = mid;
        } else {
            left = mid + 1;
        }
    }
    return left;
}