package recursion;

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));

}

}