class Solution { public: int mySqrt(int x) { long long l=0,r=x,mid; while(l<=r) { mid=(l+r)>>1; long long ans=mid*mid; if(ans<=x && (mid+1)*(mid+1)>x) return mid; if(ans>x) r=mid⑴; else l=mid+1; } return mid; } };