278. 第一个错误的版本(java)

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

public class Solution extends VersionControl {
    public int firstBadVersion(int n) {
        int l =1;
        int mid =l+(n-l)/2;
        while(l<=n){
            //isBadVersion()函数在父类中已经定义了
            if(isBadVersion(mid)){
                n=mid-1;
            }
            else{
                l=mid+1;
            }
             mid =l+(n-l)/2;
        }
        return l;
    }
}