原理是二分法不断迭代:
取max为指定值target,min为1,精度要求m;取min和max的中点mid,当midmid>target,把max设定为mid;当midmid<target,把min设定为mid。然后max和min求出新的中间 newMin。
结果就在mid和newMid之间,并不断逼近最终结果,当newMid-mid的绝对值小于m时,结果即为所求
【代码】
package practice;
public class Sqrt {
public double method(double target, double m) {
double min,max,mid,newMid;
min = 1;
max = target;
mid = (min+max) / 2;
do {
if (mid*mid<target) {
min = mid;
} else {
max = mid;
}
newMid = mid;
mid = (max+min)/2;
} while (abs(mid,newMid)>m);
return mid;
}
public double abs(double a, double b) {
if (a>b) return a-b;
else return b-a;
}
public static void main(String[] args) {
System.out.println(new Sqrt().method(20,0.0001));
System.out.println(Math.sqrt(20));
}
}