leecode-69. x 的平方根

69. x 的平方根

   public int mySqrt(int x) {

        if(x == 0) return 0;

        if(x <= 3) return 1;

        long ans = 1;
        long L = 1,R = x;

        long M = 0;

        while(L <= R){

            M = (L + R) / 2;

            if(M * M <= x){
                ans = M;
                L = M + 1;
            }else{
                R = M - 1;
            }

        }

        return (int) ans;

    }