[leetcode 69] Sqrt(x)

int sqrt(int x)

class Solution {
public:
int sqrt(int x) {
if (x <= 1) {
return x;
}
int l = 1;
int r = x;
while (l <= r) {
int mid = l + (r-l)/2;
if (mid == x/mid) {
return mid;
} else if (mid < x/mid) {
l = mid + 1;
} else {
r = mid - 1;
}
}
return r;
}
};