package test;
public class RecursiveTest {
/**
* 递归实现
*
* @param n
* @return
*/
public static double recursive(long n) {
if (n == 1) {
return Math.log(1);
} else {
return Math.log(n) + recursive(n - 1);
}
}
/**
* 非递归实现
*
* @param n
* @return
*/
public static double directly(long n) {
double result = 0;
for (int i = 1; i <= n; i++) {
result += Math.log(i);
}
return result;
}
public static void main(String[] args) {
int i = 5000000;
long test = System.nanoTime();
long start1 = System.nanoTime();
double r1 = recursive(i);
long end1 = System.nanoTime();
long start2 = System.nanoTime();
double r2 = directly(i);
long end2 = System.nanoTime();
System.out.println("recursive result:" + r1);
System.out.println("recursive time used:" + (end1 - start1));
System.out.println("non-recursive result:" + r2);
System.out.println("non-recursive time used:" + (end2 - start2));
}
}
|
