First Bad Version

给一个API, 找到一个返回false的数. 这个就是二分查找.

/* 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 i = 1;
        int j = n;
        while(i<=j) {
            int m = i + (j-i) / 2;
            if(isBadVersion(m))
                j = m - 1;
            else
                i = m + 1;
        }
        return i;
    }
}