First Bad version

/* The isBadVersion API is defined in the parent class VersionControl.
boolean isBadVersion(int version); */

public class Solution extends VersionControl {
public int firstBadVersion(int n) {
if (n < 2) {
return n;
}
int left = 0, right = n;
while (left + 1 < right) {
int mid = left + (right - left) / 2;
if (isBadVersion(mid)) {
right = mid;
} else {
left = mid;
}
}
if (isBadVersion(left)) {
return left;
} else {
return right;
}
}
}