long long 范围内的开根

int Sqrt(int x) {    if (x == 0) return 0;    double last = 0;    double res = 1;    while (res != last)    {        last = res;        res = (res + x / res) / 2;    }    return int(res);}

 浮点数的开根

double fun(double x) {    if (x == 0) return 0;    double last = 0.0;    double res = 1.0;    while (res != last)    {        last = res;        res = (res + x / res) / 2;    }    return res;}

 

java 大数套牛顿迭代

import java.math.BigInteger;import java.math.*;import java.math.BigInteger;import java.util.Scanner;import java.util.*; public class Main{    public static void bigSqrt(){         Scanner cin=new Scanner(System.in);          String s=cin.next();          BigInteger remain=BigInteger.ZERO;          BigInteger odd=BigInteger.ZERO;          BigInteger ans=BigInteger.ZERO;//          remain=BigInteger.ZERO;//          odd=BigInteger.ZERO;//          ans=BigInteger.ZERO;          int group=0,k=0;          if(s.length()%2==1)          {                  group=s.charAt(0)-'0';                  k=-1;          }          else          {                  group=(s.charAt(0)-'0')*10+s.charAt(1)-'0';                  k=0;          }          for(int j=0;j<(s.length()+1)/2;j++)          {                  if(j!=0)                  group=(s.charAt(j*2+k)-'0')*10+s.charAt(j*2+k+1)-'0';                  odd=BigInteger.valueOf(20).multiply(ans).add(BigInteger.ONE);                  remain=BigInteger.valueOf(100).multiply(remain).add(BigInteger.valueOf(group));                  int count=0;                  while(remain.compareTo(odd)>=0)                  {                         count++;                         remain=remain.subtract(odd);                         odd=odd.add(BigInteger.valueOf(2));                  }                  ans=ans.multiply(BigInteger.TEN).add(BigInteger.valueOf(count));          }          System.out.println(ans);        cin.close();        return;    }       public static void main(String[] args)        {               Scanner cin=new Scanner(System.in);               //int t=cin.nextInt();                   bigSqrt();              cin.close();      }}