package com.daojia.math;

public class SquereTest {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		long t1 =System.currentTimeMillis();     
		double srt = Math.sqrt(100000000.0);
		System.out.println("jdkuse:"+(System.currentTimeMillis()-t1)+":"+srt);
		double jingdu = 0.001;
		long t2 =System.currentTimeMillis();     
		double srt1 =  sq1(100000000.0,0.001);
		System.out.println("迴圈use:"+(System.currentTimeMillis()-t2)+":"+srt1);
		System.out.println(Math.abs(srt1-srt)<jingdu);
		long t3 =System.currentTimeMillis();
		double srt2 =  sq2(100000000.0,0.001);
		System.out.println("二分法use:"+(System.currentTimeMillis()-t3)+":"+srt2);
		System.out.println(Math.abs(srt2-srt)<jingdu);
		long t4 =System.currentTimeMillis();
		double srt3 = sq3(100000000.0,0.001);
		System.out.println("牛頓法use:"+(System.currentTimeMillis()-t4)+":"+srt3);
		System.out.println(Math.abs(srt3-srt)<jingdu);
	}
    /**
     * 暴力迴圈法
     * @param num
     * @param jingdu
     * @return
     */
	public static double sq1(double num,double jingdu){		
		if(num<0)
		{
			return -1;
		}
		double step =jingdu/5;
		System.out.println(step);
		double res =0.000;
	
		while(res*res<(num-jingdu))
		{
			res =res+step;
		}
		return res;		
	}
	/*
	 * 二分法
	 * 
	 */
	public static double sq2(double num,double jingdu){		
		if(num<0)
		{
			return -1;
		}
		
		double last =0.0000;
		double low=0;
		double mid;
		double up=(num>=1?num:1); 
		  mid=(low+up)/2; 
		  do{
			  if(mid*mid>num)
			  {
				  up = mid;
			  }else{
				  low = mid;
			  }
			  last=mid;
			  mid=(up+low)/2;        
		  }while(Math.abs(mid-last)>jingdu);
		  
		
		return mid;		
	}
	
	/*
	 * 牛頓迭代法
	 * 
	 */
	public static double sq3(double num,double jingdu){		
		if(num<0)
		{
			return -1;
		}
		
		double x=num,y=0.0;
	    while(Math.abs(x-y)>0.00001){
	        y=x;
	        x=0.5*(x+num/x);
	    }
	    return x;	
	}
}
 

jdkuse:0:10000.0
2.0E-4
迴圈use:147:10000.000011057207
true
二分法use:0:9999.999747378752
true
牛頓法use:0:10000.0
true