题目：

题解：

class Solution {public int mySqrt(int x) {if (x == 0) {return 0;}double C = x, x0 = x;while (true) {double xi = 0.5 * (x0 + C / x0);if (Math.abs(x0 - xi) < 1e-7) {break;}x0 = xi;}return (int) x0;}
}