Java 代码

/*
Jave中的开平方根   使用java.lang.Math类的sqrt(double)方法 
方法详解:public static double sqrt(double a) 返回正确舍入的double值的正平方根
直接调用即可  Math.sqrt(a)
*/
import java.util.Scanner;
import java.text.DecimalFormat;
import java.lang.Math;

public class Main
{
   public static void main(String[] args)
   {
      Scanner cin=new Scanner(System.in);
      double x1=cin.nextDouble();
      double y1=cin.nextDouble();
      double x2=cin.nextDouble();
      double y2=cin.nextDouble();
      double dis=Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
      DecimalFormat df=new DecimalFormat("0.0000");
      System.out.println(df.format(dis));
   }
}

C++ 代码

#include<iostream>
#include<cstdio>
#include<cmath>
using namespace std;
int main()
{
    double x1,y1,x2,y2;
    cin>>x1>>y1>>x2>>y2;
    double dis=sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
    printf("%.4lf\n",dis);
    return 0;
}