LeetCode 69: Sqrt(x)

class Solution {
public int mySqrt(int x) {
if (x < 0) {
return -1;
}

if (x < 2) {
return x;
}
int start = 1;
int end = x;
while (end - start > 1) {
int mid = start + (end - start)/2;
if (mid == x / mid) {
return mid;
} else if (mid > x / mid) {
end = mid;
} else {
start = mid;
}
}
return start;
}
}